I had the same problem. I solved it by starting with small non threatening people. You can also close your eyes and brace yourself. Remember: what matters is that you stop the D Lineman. That's basically it.
Greg's got it pretty much summed up, I play DL but when it gets down to it all you gotta do is block em, how you do so is getting lower pad level than your opponent and making them look like they're on ice skates going backwards if you can do that, then your coach will love you. Good luck this season!
