This feeling is not useful, unless you follow through with your initial impulse and go through all the books.
I feel like this feeling is partially what fuels our unsustainable consumerism and growth; we all have it, sadly.
I've done this a few times. Even if I only get value out of 20% of that collection, I wouldn't have known in advance what 20% I'd eventually be interested in.
And I do still pay for physical books too (but I don't stockpile those, and buy them when I actually want to read them)
Resources like this serve as good inspiration to learn about something new.
In ebooks, this doesn't really create a bad outcome, but I think this mindset can manifest in other aspects of our lives as well and that's where it's very much less desirable.
It was just an offtopic remark uttered with no judgement, but it's something I've been sensitive in my own attitude.
Or you can suppress the impulse and skip getting the book, then either forget the site altogether, or visit it five years later and find that it got shut down four years ago.
There have been plenty of instances where you could get lifelong legal ownership of something very valuable only if you got it at a certain time, and that time often ends abruptly without warnings.
https://www.brainpickings.org/2015/03/24/umberto-eco-antilib...
Anyway, my wallet felt it, considering I've done most of it in about 4 years with a relatively modest salary
After a few years, when trying to figure out a new thing, I conceded to turn to some book and a world opened.
Along with the discovery of O'Reilly's, and then other publishers', late shop of drm-free PDFs (which also solved the serious space problems I would have had with paper books), I went on a e-books binge, from software craft to every conceivable CS field.
I am scared to estimate how much I spent, but I'm reasonably glad of what I learned and what I have at hand.