Every time I get into a contest, I've got the same problem. I get solid solves on A and B (usually sub-5 and sub-12/13) respectively but everytime I try C, I AM STUMPED. Normally, during practice i can solve old 1500-1600 problems (like 1900-1800c for example so not too old) pretty decently. Whenever it comes to a contest its like I'm completely dogwater. What do you guys do that allowed you to get over this roadblock? Thanks in advance.

TL:DR : Im garbage tell me tips to solve C ples.