Last night I cheated on my gf.
Why did you cheat on her last night?
I have no idea, but it was nice.
Cheating doesn't happen just like that so it is good to find out why you cheated and to remember that it is bad to cheat. It will hurt your partner and could lead to the end of your relationship?
I guess I just wanted to see how it feels like to cheat.
Even if you had a good time with this other person, cheating on your gf has lasting damages and is not correct. You don't want her to cheat on you, so don't cheat on her.