For me it's about trust and the ability to relax, as well as practice. Having a good mattress protector helps, so that you know in the back of your mind that if it did leak, it's easy enough to clean up, I find that makes me less anxious. I started by hanging my butt off the bed but keeping my upper back on it, it was easier that way, and I was finally able to feely let go while laying in bed the other day which was great. Work up to it with baby steps, and drink a lot of water. Also distractions tend to help me, so I'll play a game on my phone to think about something else and it makes relaxing easier.