You just did a great job not lending your cousin.
If you feel that he/she will not pay you in the future then what's the reason why you lend money to him/her. Trust hasn't been there. It's like those banks where if you have a low credit score, they see you as untrustworthy therefore, they will not let you borrow.

Lucky for me, I didn't encounter that kind of scenario as well. Maybe because I'm good at keeping my assets, and I'm not sharing anything that's related to my money to anybody here (even to my own family ). Don't get affected if he doesn't talk to you anymore because after all, you see him as an untrustworthy person. If you are affected that much because of your decision, you can try and approach him and lend him a few dollars to at least build the trust.