I've been playing tennis seriously for a few years. I'm on the varsity tennis team at my high school. When it comes to games or tournaments, I just can't win. If I'm rallying or playing fun games I'm doing perfectly fine, my strokes are good and I hit plenty of winners. But somehow, when I'm playing in a match or something serious, I always manage to lose. I haven't won a set in the past year. I honestly have no clue what I'm doing wrong. My coach tells me I have no confidence in myself and I need to relax and stop trying to hit hard. I've been trying to do that for the past three months yet I haven't been improving, can anyone help me with this please? Thanks.