So a lot to unpack here. First things first: Has a doctor actually diagnosed a tendonitis? If so, which stage and specific tendons? Was the diagnosis based on symptoms, funcional tests or imaging?
Second thing, understand the difference between reality and perception: Tendonitis is tricky for several reasons, one of the worst being that you can't rely on your pain to guide your recovery. Some people have lots of pain but reasonably healthy tendons. Some people have little pain but their tendons are holding by a string. The best measure of recovery is decreased or sustained (but tolerable) pain while fitness increases. You might not even be that injured, but finding out demands you go through proper rehab exercises to find out and then gradually introduce play.
Third, what to actually do to get better: All sorts of strength training. Rest will not heal you. What injures tendons are jerky motions, like a floppy wrist trying to hold a broken racket against an impact. What heals tendons and tells your body they are fit for effort is pushing and pulling against resistance. Start by having a good read and following the exercises described for a couple of weeks before trying to return to play: [https://e3rehab.com/wrist-pain-rehab/](https://e3rehab.com/wrist-pain-rehab/)
Fourth, where to start with returning to play: Start small. Take a class, play a few minutes with a friend. Do a game, then rest for 3-4 days. Ease into it gradually. Always play with new balls. Definitely get a new fucking racket, preferably heavy and forgiving with a thick grip. Always new overgrips, always wash your hands with soap and warm water before playing. It's ok to have some pain (3/10) IF YOU'RE DOING YOUR REHAB. Don't stop your strength training.
Good luck, it takes a while but it's no big deal. If you manage your recovery well you can be back at 100% quickly.
man thank you so much for taking the time to write such a detailed and precise reply
this is genuinely super useful and i really appreciate it a lot honestly
gonna go read the blog post and start trying the exercises from the link you shared right now
No worries, I wish you the best with your recovery. There's a lot of good information about tendon pain out there these days but it mostly boils down to avoid explosive movement, gain strength, build back gradually.