Hello there!
I have figured that I feel low, bad, not competent, with lots of low self-esteem and bad self-image when my serotonine is damn low. Ta-da!! I figured that out while treating myself. So, what did I do? I took matter into my own hands. The doctors wanted to pump me up with anti-depressants again but they haven't worked as they should the first time I had anxiety attacks, so I googled around - professional articles from either doctor, pyschologists, nutricionists, pharmaceuts, food technology engineers... I figured I can do what the medication can in no time. So, the story goes on...
I bought L-tryptophan (capsules) - it contains tryptophan and that's an amino acid that is essential - you need to ingest it - and this amino acid produces serotonine. (You can also ingest it with food, but you have to adjust your diet to start producing more serotonine than you usually do.) So the serotonine is produced through tryptophan you also need vitamins B6, B9 and B12 - so I bought the B-complex. You also need some vitamin C and Magnesium. I bought vitamin C and Magnesium as effervescent tablets and it works just fine. So I was set. I have to tell you, I FEEL GREAT NOW! Please, do try. It's true that positive behaviour and all that crap helps, but in such a state I don't think many people are capable of it. It's perfectly natural, no side effects (except bright urine - body excretes excess vitamins). I recommend it because I feel awesome and it happened in no time.
However, in such a state, do things for yourself. Take yourself out, enjoy yourself in anyway you see fit, take up a new hobby... Whatever. That helps a lot as well. Consider yourself a parent to yourself and nurture the child inside you. I do that when I'm a lot under stress and it's awesome.