I eat soy almost everyday (plant based diet) and I'm a fuckin stud lol.

On a serious note, just be yourself and relax, if you need to pee just go pee, you're a grown man If you try to hold it in you'll feel uncomfortable, and if you feel uncomfy or tense in anyway you won't be able to enjoy or release. In the end just try to enjoy yourself buddy...generally the more sessions you do the easier it gets.