You're right, however sometimes trying to shove things out of your life may not be easy or effective. I personally decided to dig deeper and understand why I accumulated that amount of stuff in the first place.
Instead of wasting time trying to actively make this decisions and drain your mental energy, why not try semi-passive observation? I found that putting everything away and getting things that I regularly use from that pile, and getting rid of the least used part regularly (weekly, monthly, semi annually, etc.) works best.
This way also decluttering doesn't feel like swimming upstream, at least for me.