Hookups-how not to get feelings and not be a jerk?

I (25M) had always just thought of sex as something that should be done within a relationship. However now that I’m out of college, and have a personal situation where I feel I might not be able to devote enough time to a serious partner, I have thought about how I would wanna experience sex while I’m still young.

There were actually a few occasions in the past where a hookup might have been possible but backed out for a variety of reasons. One time in college I was in a girl’s dorm who I felt liked me; she actually undressed into a cosplay costume while I was in the room and we were starting at each other on her bed for a while. I didn’t make a move though as even though I noticed I would have been interested in being intimate with her, I wasn’t interested in a relationship and would have felt like a jerk if I were to tell her that.

The second time, a friend had recently hooked up with someone and asked me if I were interested in having me connect me with her. I initially saw the proposal as weird but changed my mind later, by which my friend said it was too late as she had gotten a serious partner.

Third time, I was in a club while visiting a friend in a big city. I usually never go to clubs but saw a girl who looked introverted (like me) and started chatting. She talked about how she was also from somewhere far and when we were leaving, she asked if I was going the same direction as her. Honestly my friends place where I was staying was the opposite direction and just decided to say goodbye. I noticed she seemed disappointed and guys told me she probably was thinking of going all the way.

TL/DR: How came I overcome the fear of looking like a jerk when it comes to potentially hooking up?