For me it's all about the mood. Sometimes I can do b2ps without hesitation, but usually I chicken out at the last second. I've stopped only a breath or two away from the balloon exploding several times in the last month, which is really frustrating
As the others said, using earplugs and just blowing up the balloon without thinking about it helps.
I guess this depends on the size of the balloon you want to pop, but for me it helped to fully inflate the balloon (I usually use 16" Uniques), either by mouth or using a pump and just do a half knot or a clip and just have it around for a bit. Then when you feel ready, you can just undo the knot and continue blowing. That way you don't have that much time to build up the anxiousness before it pops.
Personally I prefer U16s. I try to b2p smaller balloons sometimes, but most of them gets really difficult to blow towards the end and I just give up.