I took the same lesson from clearing out my parents things. What I'm trying to do now is to clear out incrementally. Doing a full sweep is way too easy to defer to future me and therefore never happens, so I try to do a small amount regularly. My big box of cables (another recent thread here) is a rich source of material that will keep me busy for a while. Pretty sure nobody will appreciate going through that.
Also just trying to notice things around the place that I really don't need, books I'll never read again, boxes that have not been opened for years. A little bit at a time. Removing each one gives a small sense of achievement.
Yes. When one is young it is difficult to appreciate this, but later in middle age this becomes very precious. Store everything, your future self will be happier for it.