Last rep problems

[GeoS]

I seem to be missing out on muscle building because at the point I reach muscle fatigue, I am not really able to do another 2-3 reps. This also makes it hard to progress to higher weights. Instead I've begun to move to a lower weight and do another 2-4 reps after I fatigue, but I still feel I've been missing out on muscle gain. Am I doing the wrong type of routines for muscle type? How do I figure out a better one?
-Usually work out daily, rotating from chest/back/abs, shoulders/legs/abs, arms/abs
Usually 8-12 reps, 2-3 sets per muscle group

[RK19]

training to failure isnt good,doing it everyday is worse (stimulate dont annhihilate)

if your only managing say 5 reps of an 8 rep set, youve chosen a 5 rep max weight when it should be around a 10rm weight so as to complete the set, see what i mean?