You're not always going to remember what happened to make you feel this way, what you are going to remember is what you felt, and how you dealt with it. Did you let it bore holes through your innards, like some potent acid, or did you accept it, then unfurl your clenched fist to release it into the ether? Yes, those emotions will come again, and again you will have to make the decision, but what you may take into account is that it will never be the same thing which causes it; consider the bad emotions as part of the experience, without them, there would be no experience. You must experience grief to revel in joy. They don't lie when they say that the secret is to always find the silver lining, and though sometimes it may blend well with the grey of the cloud, it is present, waiting for you to discover.
You could take a sad song and make it better, or you could ride out the wave of melancholy on the notes of that song, until eventually it pulls you under and you drown. The truth is, eventually, you're going to have to pull yourself out of it.
However, if that wave breaks, and leaves you in pieces along the shoreline, I promise that I will be there to pick you up and put you back together, every last piece. And I'll stay with you until all the wounds heal, and even afterwards, because you are worth every second spent on you. Eventually, you'll start to find the silver lining without help, and my presence will become redundant, but until then, be assured that you could never be rid of me.