This is difficult work - congratulations on having the courage to start it.

Look into CBT and {DBT}(http://en.wikipedia.org/wiki/Dialectical_behavior_therapy). These are best done with a therapist (someone with an outside view, training, and experience), but I've gotten some use out of reading materials on my own. You've already done the first part, which is identifying the thoughts that trigger meltdowns. The next steps are figuring out what thoughts are more accurate and helpful, and then training yourself to habitually have those thoughts instead.

Note that DBT was developed for people with borderline personality disorder, which sounds scary if that's not you, but can be useful to anybody with emotional regulation problems.