Men are inherently selfish.
All men (and most women) are capable of cheating. I thought I would have cheated on my ex husband before he cheated on me, but after 15 years together, he did and I didn't.
That it is far better to be single than in most relationships. In my opinion, most women in relationships are with men who aren't good enough for them.
That far too many people are dating or in relationships when they aren't emotionally ready for them.