Right. It's not dissimilar to how Mutant powers often first coming out. It's due to triggering events, stressful situations, heightened feelings. What I try to work on with the people I train is to tap into positive feelings to trigger their powers instead of negative ones.

[ It's not like it's easy. But nothing worthwhile ever is. ]

Negative emotions are harder to control than positive ones. And you should definitely keep going with the meditation, as it gives you a much better handle on yourself, and makes it easier to get over negative emotions.