1. I was in the heat of the moment.
2. It just happened.
3. I was bored.
4. It just seemed like the thing to do.
9. Its exciting, adventurous.
10. I wanted to make up after a fight.
11. I wanted to get rid of aggression.
12. I was under the influence of drugs.
14. I wanted to express my love for the person.
16. I wanted to show my affection to the person.
17. I felt like I owed it to the person.
18. I was attracted to the person.
19. I was sexually aroused and wanted the release.
21. It feels good.
22. My partner kept insisting..
31. I was tired of being a virgin.
32. I was horny.
33. I wanted to feel loved.
39. I was competing with someone else to get the person.e.
54. Its fun.
64. I felt sorry for the person.
77. I wanted him/her to stop bugging me about sex.
87. It became a habit..
103. The person was too hot (sexy) to resist.
121. It was expected of me.
135. It was a romantic setting.
148. I wanted to break up a rivals relationship by having sex with his/her partner.
170. I wanted to breakup anothers relationship.
183. I wanted to say Ive missed you.
184. I wanted to celebrate a birthday or anniversary or special occasion.
200. The persons physical appearance turned me on.
211. The person really desired me.
212. The person was really desired by others.
217. The person had a desirable body.
227. I knew the person was usually out of my league.
I think those ones apply to me, sometimes to the same person