Has someone here picked a musical instrument seriously for the first time in their 20s and managed to self learn? If yes, it would be helpful if you could point to resources that were helpful to you and any daily practice schedule you followed? I have tried learning piano and I found a lot of stuff irritatingly hard to get right and got bored. Like for some reason I am not able to transition to other keys well when I…
Piano fingering technique is very important. That's not just which finger hits which key, but also the posture of your finger. That could be what's straining your fingers and giving you trouble reaching keys.
I found a local piano teacher and took weekly lessons. The piano teacher caught these bad habits like finger technique, but also how hard to hit the keys and other things that I wouldn't have noticed on my own.
If you are set on self-learning, getting a few lessons every once in a while will help you stay on track.