Every time someone lets you down is another opportunity to beat yourself up with thoughts like “that’s what I get for trusting”. You can then close yourself off and make others prove their trustworthiness before you let them in.
In my experience neither those thoughts not that strategy is very useful. You end up closing yourself off to many great opportunities that require you to make the first gesture of trust. The best way to build someone else’s trust in you is to make a leap and offer your trust first.