I am lucky in that when I first set up my now permanent layout I had waited to start construction until I had lots of financial freedom.
At the beginning I had yet to hone in on things I like. Now I only run "Hi-Rail Scale" equipment and concentrate on Steam/Diesel transition New York Central. Although I do have a fondness for some C&O and my collection reflects that.
I've sold non-scale items, a scale set of Rio Grande Alco PA's etc to swap them out for things I'm more interested in.
I have a modest layout, one that was kindly designed by a fellow forum member years ago. With only 3 contiguous loops and only two being main-lines I often feel overwhelmed by my choices but considering my slow and deliberate purchases I chalk that up to me needing more main-line track!
Sometimes I get overwhelmed at the prospect of running them. Having paid so much for many of these models, many with delicate pieces, temperamental smoke units etc at times I find myself looking for issues or getting caught up worrying too much about certain things to enjoy running them. Sometimes if I'm switching in the yard with a train parked and powered I can't shake the idea that I'm burning the parked trains smoke unit. It's not terribly often, but enough that it stops me from enjoying my trains to their fullest.