I've started taking guitar lessons recently. A bit late, you might think, but it's better late than never. And anyway, I did have a brief fling with playing the guitar back when I was fourteen or so, so I'm not starting from scratch. I was pretty much starting from scratch, though, because I remembered all the theory but had absolutely no way of applying it. Lots of people will tell you about permanence of muscle memory; my muscles apparently got over it and started going steady with something else (hello Scheidegger Ten Finger Touch Typing Course) many years ago and didn't look back.
In the past I've also taken writing lessons. That's something else I've done for a while too – I started writing Science Fiction when I was six. So I've met writers and guitarists, and writing teachers and guitar teachers, and I've discovered they are very different people.
(The picture is of Robert Plant playing Jimmy Page's guitar at the sound check, Hiroshima, 1979-09-27. Photo by Koh Hasebe.)
I have to say that getting the calluses back was the second most painful thing I've ever had to do, too. It was worse than waking up from the anesthetic before they started the pain control that time after my cancer op, but was nowhere near as bad as breaking one of my toes on the furniture a couple of years ago. That hurt. In fact the bloody toe hurt more than the time I broke my finger when the fiberglass hood of my Corvette slammed shut on my hand. I'm actually surprised I still have fingers after that. And my finger didn't hurt too much, either, until the fact that the idiot emergency room doctor missed the fracture meant that it didn't heal and then it really started to hurt about a week later. Anyway, I digress. What I mean to say is that I'm not really that much of a wimp, but rubbing your fingertips on cheese-wire for an hour a day is a shabby way to treat them.
Of course, they've forgotten about it now, due to their poor muscle memory. I can still type with the calluses, too, but I can no longer turn pages in a book. Anyway, that's probably a topic for another day. (And it's not a hint for a Kindle for Christmas.)
Now, your writers don't seem to like writers. The writing courses I took were a couple of Adult Ed ten-hour classes, and it both cases the minor-league writer teaching it spent the entire time telling us that it's hard to get published, editors hate you, you'll fail immediately and constantly and the very first words of your cover letter will suck so much that editors will single them out to share on their blogs about how stupid writers are. Then the next week you hand in your homework and the teacher tells you you'll never make it. (Though by this time the sting is wearing off.)
I've met non-teaching writers too, particularly at the Worldcon. The professional writers on the panels have their books in front of them and occasionally, whatever the subject of the panel, make remarks to each other about how successfully they've put any writers in the audience off submitting anything to anybody. There's also always one panel there where professional editors read out gems from their slush pile and everyone laughs. The savvier editors pick out sex scenes, because even an ok sex scene sounds thoroughly stupid when read out by someone who is feeling more sarcastic than sexy. A few of these torrid passages and the audience is laughing like drains with the editors and wondering how they put up with having to deal with writers all the time. Poor things!
On the net, blogs cover the subject of why you shouldn't ever write anything. You can buy demotivational calendars and t-shirts to help you stop writing. Ex-writers tell you how happy they are to not be writing. Agents publish things about how life would be great if they didn't have to meet writers. 
Now, how about guitar players?
My guitar teachers wanted to teach me how to play and have never yet said I'm not going to be famous. It's possible that's because they know I haven't actually made the assumption I will be famous, but there is an amazing sense of relaxation induced by having a teacher who wants you to be as good as you can be, rather than spending half the lesson telling you all about how you'll never be as good as an editor wants you to be.
Also, although I haven't played it for many years, I've had my guitar in its case just sitting around the house since I was a kid (minus a few years it spent with a friend of mine). So I can tell you that regular guitar players, on seeing your guitar, exhibit one or more of the following behaviors:
• They want to play your guitar
• They want you to play your guitar
• They want to get their guitar and the two of you can play guitar together
• They want to talk about what songs you know
• They want to teach you how to play other songs
• They want to lend you their guitar
• They want to lend you their electric guitar
• And their amp
• And their effects pedals
• They want you to come to their parties so everybody can play guitar.
When I first started learning, back in the approximately 14 year-old days, I used to go to a jazz club with my mum and dad every couple of weeks. In those days I knew my electric guitars fairly well – even girls have a bit of the trainspotter gene in them – and I asked the (awesome, I recall) guitarist in the house band there once about his battered Stratocaster. He told me its serial number, which was so low it made my jaw drop, then handed it to me and asked if I wanted to play it. In the club, between sets. At fourteen.
Yay for guitarists.
(By the way, if you missed the punchline there because you switched your brain off in outrage that a 14 year old was hanging around a club where people, like, drink beer and play jazz and stuff, then you're either much younger than I am or American, or both. And I pity you.)
Now, I realize some of this difference is due to the nature of music versus writing. Knowing the standards is the criterion for basic guitar playing. Your new friends probably know Smells Like Teen Spirit and Hotel California and House of the Rising Sun, not just to listen to, but to play. On the other hand, at least currently and in the West, originality is the major criterion for writing fiction.
So you aren't going to get a conversation like this:
Person at a party: Hey, you write? Are you familiar with War and Peace? In English? I've been working on the middle section a lot recently. Let's go write. If you handle the paragraph breaks I'll show you these adverb inversions I found.
And some of the difference is due to the indivisible nature of writing. You can't write in harmony. But the image of a writer as a skivvy-clad loner nursing a bottle of scotch while piñata-ing their muse until the words tumble out in a broken heap can only explain that one small part. It doesn't explain the attitude to other writers, or the weird way that everyone assumes you want to be J.K. Rowling, and that furthermore, you deserve to be put back firmly in your place for even looking like you might. Do they think writing is a zero-sum game where only a few can be winners so it's in their best interests to nobble the competition? Could be – the people who are *for* Creative Commons licenses are generally *not* the people I discuss above.
At least, I'm fairly sure that guitarists don't go to conventions of music listeners and the guitarist-panelists talk about the time they went to somebody's house and asked them to play a song and the beginner played House of the Rising Sun hahahaha, and then the audience all laugh like drains at the loserness. How dare he think he's going to be Stevie Ray Vaughan! Loser!
 Note: I exempt everybody on Live Journal, some people on Yahoogroups and the regulars of rec.arts.sf.composition from all the negative comments about writers.
 Though now I've thought of the concept I might try.
Edited to update a link and remove the t shirt link.