Letting the ones you let go go

I folded 3,4 and 10,4.
And I've been kicking myself all weekend for it.
In the first case, I played five hours of nickel, dime with some friends. I came out a winner, and yet, all I could think about was the pot that escaped me.
I had 3,4 and the flop came 2,3,4. I check-raised in the hopes that the two callers would have the straight just yet. I got raised back. The other guy insta-called. Shit.
I knew they had a straight, probably both, even though both were inexperienced players and would call with a pair at that point.
So I thought about it and folded.
And a 4 came down.
Had I given it some thought, I would have realized that I had six outs, giving me roughly 25 percent to make my hand, and the pot odds were still great, with $1 to call a pot of $7. But I didn't and I folded because I was spooked.
I would have taken down at least $25, I'm sure, with that hand.

In the second, I was on Pokerroom late at night, jumping around, when I was dealt 10,4 with the first hand. The guy raised .25 cents and I folded despite already posting my blind. Again, pot odds dictated that I call, but I didn't, and a full house came down for me. The guy went all in, and I would have taken down $75.

I believe it's harder for me to let these go than the bad beats. In fact, I lost $20 on another hand because I suffering from tilts far worse than a bad beat tilt.

You think too much about the money you could have had. It's dangerous, of course, to think that way because it encourages far too much fishing in the future.
But I can't let it go right now. Hands like that are old lovers, when we only think about what could have been, and the fact that most of the time things really suck. Like with 10,3.