I personally think it is always tempting to reveal certain information when someone tells you not to tell someone else something. You may have to use constant self-discipline to prevent yourself from giving this information away.

Okay, so I think you need to try a few methods here.

First, what about asking your friends to not tell you things that they don't want other people to know for about a week or two? This could be a drag for awhile if you enjoy hearing secret information or gaining the confidence from your friends, but it could make you more aware and appreciative of this information, and thus more protective.

You could also try the path of negative reinforcement. Do your friends find out what you did and then get angry at you? I think you have to remember these negative reactions and the people that you hurt or the people that get very angry when reveal what they have said in secret.

It must be a pain to have your friends mad. So maybe their anger can help to motivate you to keep private information private.

One other method might be to get into a habit where you take a deep breath and count or tap each toe (just some action that you can repeat over and over) before you speak to someone in a situation where you feel the need to give away secret information. You may even try to do this all the time so that it becomes second nature and you have time to think built into your conversations.