Doesn't matter if you are single or already in a deep relationship, you should know what not to say to your man. 10 things girls should never say to guys. So the next time you 're with your boyfriend or a guy friend, remember to avoid making him feel less like a man. “No regrets” is my motto – and a very popular one at that – but often we need some guidance to learn not to do things we regret. The worst.