Re: How can you tell if somebody has bad intentions?
Well, it happens to different people at different times. For me, it happened super early, but that's because I watched my mother go through cancer treatments and die when I was a kid, and the emotional and social fallout from that sort of thing will make any person a lot more perceptive. For one of my best friends, it took her until she was about 14-15. For some people I know, it took them longer.
As for telling people's intentions, a lot of it is paying careful attention to what they say vs. how they act and how well the two match up. You don't have to actively call them out on discrepancies, but definitely take note of them, because often if what they say doesn't match up to what they're doing or how they're acting, you need to trust that the ACTIONS are the truth. Words can be twisted any way you want them to.
But I'm guessing is that you've chattered about something personal and then have had someone either use it against you or throw it back in your face. This is purely something you need to fix, because sometimes you just really need to look out for yourself.
I'm fairly honest myself, and will candidly talk about things like my mother's death and some of the more awful things that have happened to me. But I also know that I have the emotional fortitude to handle any backlash or awkwardness that comes from those topics.
You probably need to go through your head and categorize out what you should share and what you shouldn't. You don't have to stick the list completely, but being like "This part of my life, strangers are allowed to know about it", "this part, this part and that part are OK to tell acquaintances and co-workers" and "I'll keep THIS part for close friends and family - people with established trust".
I hope that helps?