Something that always keeps coming back to me is the phrase "There ain't no such thing as a free lunch".
Exactly. And it's not just a smart-sounding phrase—it was proven mathematically in 1995 by Wolpert & Macready. I remember referring to their paper when I was doing research back in the late 90s.
[Santa Fe Institute] William Macready, David Wolpert — No Free Lunch Theorems for SearchThe full paper in PDF format can be found in the above link.
i was introduced to that phrase as TANSTAAFL in
The Moon is a Harsh Mistress by Robert Heinlein.
awesome read if you have yet.