they help me more out of small ruts. i also notice benefits for bigger episodes, but it's not enough to fix them, and good habits are harder to maintain the worse you feel.
running/exercise is awesome when i'm a bit down, but hard to finish out when i'm really off, or even if i do, it may only help a little (if at all). i stopped a run midway through today because i was just too overwhelmed with sadness, emptiness, and lack of motivation to continue.
trying to maintain a healthy diet is good though. if you emotionally eat (like me), aim to be healthy when you can, ie. for breakfast and lunch if you stress eat junk at night