1. Cheat sooner rather than later
I would rather have someone cheat on me early on in the relationship than 5 years into a marriage, where children are involved. Allow the person to do as they please and it will show you a lot about them.
2. You were never into me
Simple- you cheated on me? That's right, now I can leave without ever looking back because I know that you never loved me the way that I loved you.
3. I can do better
No one deserves to get cheated on, so at the end of the day you re-confirmed my assumptions that I can indeed do better than a cheater. Anyone can.