Oh Jeremy, I sympathize with you. I don't know what the fix for tendonitis is - I have it too, it's been three months since I've played my instruments, and it's been a very miserable three months (the pain doesn't bother me that much, it's the silence). I urge you in the strongest possible terms to take this seriously, and don't play until you've dealt with it. Playing through the pain will make it worse.

As for how to deal with it - neither rest (i.e. no music, trying to minimize other stresses) nor wearing a splint nor taking ibuprofen frequently for a few weeks did much for me. I am now in physiotherapy, which mostly involves muscle-building exercises, also some ultrasound treatment, electroshock therapy (that's probably not the real word for it), and acupuncture. Also, my PT stresses the importance of applying ice as often as possible. Her main idea is that the tendons get hurt because the muscles aren't strong enough to do the work you give them, so the tendons have to share the load, so the main fix is to build the muscles. In the process the tendons keep getting inflamed again, so you need lots of ice. I think I am seeing some progress since starting physio.

Your question mentioned "coping", so if you're also asking about how to deal emotionally with not being able to play: the first two months I was depressed, and dedicated the time I would normally spend on my music to lying on my floor crying. I have now picked up a bit. What I am trying to do is find hands-off ways to work on my music, and some of these might be options for you. Could you study theory? Compose lyrics? Practice intense listening?

For myself, one of my big guitar weaknesses is that I started by just memorizing the chord shapes for the popular chords rather than thinking about the fretboard in terms of individual notes, or thinking about why the chords are constructed in the way they are. So my project now is to become intimate with the individual notes on the fretboard. One way I do this is to play mental guitar; I just read pieces of sheet music and visualize where each note is on the fretboard. Also, I have made up flashcards to help me learn the fretboard inside and out: sheet music to fret position, fret position to note name, "name the notes that are on the fourth fret from high to low", "what common chords contain this note", and so on.

Maybe you already know all this stuff well; but even so, you can probably find something to be working on without touching your guitar. If not, why don't you try immersing yourself in some style of music that isn't currently part of your repertoire?

I hope this helps, be brave,

Marion