If you are going to portray yourself as Alpha you better be able to deliver the goods when you get her in bed. A friend of mine is dating a guy who put himself out there as being so Alpha that he was going to rock her world. They finally slept together and when she came into work next she went out of her way to tell me what an epic fail their sex was. He could not kiss worth a damn, mangled her pussy with inept finger banging technique and the capper: he had a hamster dick. She said if he hadn't talked himself up so much, how he was going to fuck her like she's never had it before, it would not have been so...insulting (her words, not mine). She nexted him immediately.

TL;DR. Put some work into your sexual game. If you have a hamster dick don't pretend your Alpha.

Edit: some clarification. 'Chet' her told my friend 'Jennny' within hours of meeting her that she should go home with him because he would give it to her so good she'd need an ambulance home, etc. I was out when he was there and he made it seem like he was capable of extreme porn star sex. Jenny was just a little incredulous when it turned out "his dick was the size of a chapstick tube." He obviously got confused about the concept of under promise but over deliver.