I think it's a mental thing. I have that problem of losing (or barely winning) to players that shouldn't even get games off of me. I bet that ur one of those people who only play ur best against really good players. And then when ur faced w/ a week player, the pressure builds up b/c u're expected to win; and then if u lose, it's like the worst thing in the wolrd and it carries on into your other matches. that's how I am on my school team. Anyways, It pretty much comes down to being match tough. Play a lot of matches. What I found to work (especially today) against lower players is slicing. They tend to hit short balls to u and so topspin isn't the best choice unless ur at the proper hitting position. So slice like crazy! and also, u have to realize their weeknesses from the beginning. Usually against lower players, their miss**t in the warmups will be the miss**t of all the match. So aiming there will help u finnish the match quicker. I hope that helped.