Let not get it twisted, where there is no risk, there won't be rewards, so as a gambler there is a need to take the risk as much as possible, but also we have to avoid regret as much as we can also, since both risk and regret are two different things, but the thing there is that I will not regret for not taking a bet because I have not risk anything in that order and since we have to understand what we need and what is ours which are two different things, when you risk a stake on a bet, that point you become involved with that game, but when you are not risking any money on that such a game, you will not be involved and highest is to just watch and enjoy the game and regardless of which direction the match ends you will not be overly affected by the outcome, so don't let greed deceive to regret and think that your predictions could have won you such a bet.
I agree with this, gambling itself is about risks so it's not something that's new to any gambler because that's what we do on a daily basis when we stake, it hurts when we lose but we are able to move on after a short while but regrets on the other hand is entirely different it you would continually beat yourself up for not taking risk that would have probably elevated you financially...the feeling of risking and losing is nothing compared to this
Yes, gamblers should know and realize this, in the sense of understanding that gambling is about risk, not only about winning but also about the risk of losing, and one of the reasons why this knowledge and awareness must be possessed by gamblers is because no matter what and whenever, risk will always be part of the game, and when we experience defeat, there will be no other way we can do but accept it.
And we can see that there are always some gamblers who still experience significant emotions, disappointments and regrets but they still continue the habit, which means that they most likely do not really understand and realize that the idea of "defeat is part of the game" is a fact that can never be denied.
On the other hand, from the two situations mentioned by the OP between the pain of experiencing a big defeat and the regret of not taking risks, I think it is much worse when you lose something, because losing an opportunity will only end in regret but not end in losing something you have.