Wanting to be a better lover

I have, mostly, always been top. I am told I am good to my partners and I am sure to get them off before I am done (with few explainable exceptions}. I am also told I am a bit large of junk for some of them and I can get a little aggressive during sex. I am always worried that I could be doing better, I feel like there are some expectations of a bottom that tops can't understand. Does anyone have anything they always wanted a top to know but never told him?