Sometimes good sex or feeling comfortable with sex is having a partner that you feel comfortable, safe and cared about with.

Sex and any sexual activity is just as much mental as physical.

I struggle with my partner sometimes because I get insecure about my apperance, the movements, the touch, the moment is right but because mentally I am not completley enjoying it because I am worried about how I look or how my partner sees me the sex isn't as enjoyable.

I also had past traumas I had to work through before I could even begin to think about any sexual activity, I had to learn to heal the wounds and also be comfortable with my sexuality and myself before I was able to enjoy things.

Setting boundaries is a great idea, don't let anyone pressure you into sex until you feel comfortable with them, or your in a relationship, or whatever boundary works best for you and your needs.