Self-handicapping is when someone puts extra obstacles that get in the way of their own success. For example, if someone wants to do well on a test, they might stay up late studying, but they might also stay up late partying, which would act like a "handicap" to their success. It's like they are intentionally making it harder for themselves to do well. It could be an excuse for why they didn't do as well as they wanted because it's not their fault - it's the handicap's fault.