Opportunity cost is the price that's paid for not doing something that you could've done. So, if you go to the concert it will cost you $50 - but the opportunity cost is that you can't go to the library and you can't watch the football game. It's an important concept when making decisions.
It can also be taken to the extreme. I'm convinced that my daughter thinks she is constantly paying too high of an opportunity cost - she always thinks there is something better that she could be doing. When we're at home she wants to be out doing something. If we go out to do something she wants to do something else or be back home. She's never able to enjoy the moment and what's happening in the present. If we're out having fun, she still doesn't have fun because she's too worried about what else she could be doing.
I have a similar problem. There are, probably literally, over a thousand to do/task management apps. I use one for a week and then think that there has to be a better one out there. So I start searching for a better one - I try them out and see if they fit my needs. They do of course because I'm just tracking tasks, but 99% of the time the method/app I'm already using is better. But, I'm constantly searching, never happy and able to use - over a long period - the same app.
My point here is that you need to think of opportunity cost before you make a decision, but once decided live in the moment and quit thinking about what you might be missing out on. Honestly, your probably putting a higher price on the opportunity cost than what it's really worth anyways.