Tips for BJs

i’m not a bj person, maybe because I had not so great experiences with my old partner. I’m with someone new and he’s so patient with me about it. I do it on him every now and then & it’s really not bad at all with him. He’s so clean. But because of my other experiences i’m scared to do it. Anyone has any tips of what might calm my nerves or how to be better at it? Basically bj for beginners/dummies lol