They probably won't help you anyway. If your anxiety is really bad then I don't see what beta blockers are supposed to do, they're meant for performance anxiety for people who need to be really calm (sharp shooters, snooker players), not people who are physically terrified of the world.
Why did you get a prescription for them if you're not going to take them? I don't really see the point in that. You may as well try them and see if they help but I very much doubt you'll see much of an improvement. If you have chronic anxiety you'll probably get more out of an SSRI (not that it worked for me) or a benzodiazepine.