If you're emotionally high or low on a regular basis then you probably need to stay away from gambling period as you will probably throw yourself into major depression once the high wears off, or go deeper into depression while the low is happening. Gambling is a bif roller coaster with lots of highs and lows and you need to be emotionally stable to handle it properly.
I agree, not only if you are depressed, also if you are sad or tired, anything other than being in as emotionally neutral a state as possible. And if you are a person who tends to get carried away by emotions, the best thing you can do is stay away from gambling.