While doing interviews I got asked if my experience from a project more than 10 years ago is still relevant. At first I was about to dismiss it as a simple way to reduce the number of topics during the interview but then it clicked on me.
Roles that require knowledge work and also require deep focused work it means that anything that improves or changes the thought process is relevant; specially if it was something that was hard at the moment or completely new. For example new technical problems or paradigm shifts are always relevant. Also after these kind of experiences is really possible to look back to previous experiences and improve the thought process even further. Whenever something was difficult it means at least a lesson was learned there, although it might be unconscious at the moment but after a while it will become evident.
So in short:
It is relevant, it compounds, it moldes my thought process, there were lessons to be learned.
All your experience, even going back to school compounds to what you are capable of doing today. Do not discount your prior experiences, even if they seemed to be failures. You have learned from them all.