Had my share of bowhunting failures the 1st few years as I was mostly self taught but never let it make me wanna quit. It actually made me a better hunter because I learned how to bowhunt the RIGHT way(not saying yours isnt right)
Heres a few things that I changed about my habits and gear that I believe has prevented me from losing a deer in the last 7 years and probably killed close to 20 cleanly since.
1st and foremost I did not shoot until the deer close enough that I KNEW, not thought, my arrow was gonna go exactly where I was aiming no matter what. At 1st it was 15 yds then I felt comfortable out to 25yds.
I keep my gear simple, I use a bisquet rest, 1pin fixed sight, fixed heads, and I leave my quiver on my bow , less moving parts , less chance of something going wrong. JMHO
I made sure my bow was tuned properly so that my arrow was flying and strikeing the deer in a perfect straight line. If you dont know how to paper tune or "walk back" take it to a pro shop and have them tune it for you.
Another big thing I believe in is going heavy with arrows, at least 400gr TAW, and draw weight low enough so you can draw with out raising your bow up at all(speed means nothing to me) and I personally only use cut on contact fixed heads. my choice is sonics and the penetration at all angles is amazing!
Practice shooting from all kinds of weird positions with heavy clothes on at really far distances , so when you get a deer at 20yds its like a chip shot.
Dont quit! hang in there and good luck.