How can one overcome frustration and regret?

Yes, I know, one would say "be happy with what you have/ actually is, instead of focusing on what you don't have/ what should have been". But is it so easy?

It is again tied to the frustrating missed opportunities I have been blogging about almost two years ago, to the fact that nothing happens if you don't write and to me claiming that I don't care anymore, as advised above... just that I actually do and I just pretend I do not.

We do have some amazing stories going on "Before the Mast". But they could have been better, and I can't escape this thought. 

There are threads which are going on in 3-6 characters and NPCs, written by 1-2 people, when they should have involved 10+ characters and NPCs, written by 5-6 people, just because there are people who keep away their characters from threads where it would be natural for them to be a part of (or post 1-2 times then vanish). Their characters whom they keep away from the story won't leave a mark on it, when for the character's personality and/ or role in the story it would have been normal to do it. Nevertheless, even if they aren't explicitly involved, they still are involved "somewhere in the background", ie passively the outcome of the story the writers didn't want to introduce them into will affect them too. If the whole ship is taken prisoner, they would be numbered among the prisoners, as long it isn't written that (and how) they have succeeded to escape believably. They can't be two days later happily chatting in a tavern scene, as if nothing had occurred. One doesn't live in a time bubble.

But most often, they aren't chatting two days later. Those who are counting their number of threads and don't take more, even if it would have made sense for their characters to be involved, at least are good at keeping track of what happened and this doesn't happen. What happens more frequently is that a writer's hiatus (or vanishing without words) is usually lasting longer, and the characters are nowhere to be found when they are needed. I keep imagining how the ongoing adventure threads would sound if everybody was there, as they should have been, and it makes even lonelier the endeavour of writing it alone or with only one writing partner. And the "It shouldn't have been this way!" gives a bitter taste to stories I actually enjoy, the taste of  the the frustrating missed opportunities. (Then others come and say that roleplaying is an activity which should have been done with others, not alone... as if I preferred it alone vs. with others!)

I keep wondering how to deal with it... How not to think anymore at how the story should have been developed and what chances the others were missing.