Do you ever switch up your weight training methods? Try Static training, the next time you lift weights. It builds the endurance of your muscles, a factor that is not often targeted but should be!
For static training, hold the weights out in a specific position for an extended period of time. For instance, raise a pair of dumbbells upward with your arms straight until they are at shoulder level. Hold the weight at this point for several seconds...long enough to make your muscles shake. Lower and repeat.
You can also do the same thing with a curl...hold the curl at midpoint for several seconds per set. And triceps can be targeted as well, hold your pushup at the bottom for a few seconds. Even the quads can be trained in this way, holding a squat at midpoint or the bottom of the squat for a few painful seconds! Feel the burn!! Change the way you work out, change your body!!
Listen closely: the only time it's too late to change yourself is when you're dead. Until then, you're simply making excuses or lying to yourself.