Into anything you are involving for long time, definitely you will get depressed at some point of time; there could be no exception like gambling/trading etc. But, people love to do something for long-term when it remains profitable but unfortunately both trading and gambling may not remain profitable if you are over engaging with that. This must be the another reason why I am seeing both online gambling and day-trading are very much similar to each other.
To end your day profitable, you must gamble or trade only for limited period of time. But, you can prepare yourself in all other times but the actual part of trading or gambling should be only in limited period of time. This is how we can manage trading/gambling profitable regardless of it will be turning lucrative over the time.
If we are going to talk about "lucrative" I have to say gambling. Because in gambling you can bet on 9999x chance to win and you can win it, unlikely but you could still do it, in trading it is nearly impossible and in fact I do not know anyone ever that made 9999x return on investment, that may have happened before in history but we know how unlikely it is whereas at least one person in the world somewhere wins a 9999x bet somewhere. Which is why the "lucrative" side is definitely gambling for sure.
However we also have to be honest and say that gambling is a one side deal, it is skewed towards casinos and that is why it could be the most lucrative thing you do, or %99 of the time you will just lose all your money, that is more likely outcome, in trading even if you lose %50 of your money you still have some, you can't really go to zero with it.