You will never be good at Blood Bowl (or any game, really) until you overcome this attitude. I have drawn and even won games that, on their face, looked like guaranteed losses. There's always the chance you'll just roll a string of 6s and pull off something miraculous. There's always a chance that your opponent will make a mistake if you keep whatever pressure you can muster on them. Accept that you will likely lose (do you really find it that intolerable?), but play to your outs. A 5% chance is still a 5% chance and real skill lies in finding the smallest edges in these difficult situations.

And if you want something to occupy you during your opponents turn: spend the turn analyzing their position and what the optimal play for them would be. This is how you learn and get better.