It's crazy how quickly people can forget about you, until they want something from you.
— Life is Good! (@rulesolife) December 18, 2014
People are funny. Not in a kee kee ha ha kind of funny, but the shaking your head, are you serious kind of way. When you forget about someone, you completely write them off, or so you should. Forgetting about someone involves NOT asking them for any favors because you forgot about them. Let me give a couple of examples:
1. You and a close friend have a falling out and part on bad terms. Months or years later, your friend loses their job and needs you as a reference. You remember how they did you, so you tell them no. Your rationale for telling them no is that they cut you off, and now they need something from you.
2. Growing up, your parents mistreated you throughout your life and surprisingly, you didn't let it bother you. It was your parents who treated you like you weren't wanted. Outsiders treated you better than your own parents. You took that pain and turned it into motivation to better yourself. Put yourself through undergraduate and graduate school and landed a great job, debt free. You're successful by society's standards. Years later, your parents fall deathly ill and the rest of the family doesn't bother to visit them. The family gets in your ear about how you shouldn't visit them because they tell you "remember how they treated you back in the day, now they expect you to be there for them" You don't go because you know it's gonna be more of the same nonsense. You made a choice to cut toxic people out of your life and you're better for it.
If you're going to forget someone, forget them completely. Don't forget about someone, then go back to them for what you may need in the future. That's foolish, and makes you look crazy.