I completely agree, gambling when you're feeling down or unstable just makes things worse.
It's better to take a break and find a healthier way to cope, like talking to someone or doing some other activity, sometimes you are just pressured.
Most definitely.
Predicting the outcome of a game, or some games requires critical thinking and calculations too, and doing so when you're not in your right state of mind could result to having an impaired judgement, and that's really not good for a gambler. Whenever a gambler notices that there's a change in their state of mind, maybe due to excess losses or even wins, just as you've rightly said, it's best to stay calm, rest and clear your mind first, before continuing.