We tend to value items we own higher than items we don't own, even if they are otherwise identical. This phenomenon is called the "Endowment Effect" and was researched by Richard Thaler.
There have been studies by Kahnemann on this effect as well, where subjects were given coffee mugs were tasked to sell them to other participants. Participants with mugs saw the value of mugs as much higher as those without mugs ($5.25 vs $2.50).
Book - Essentialism.. the disciplined pursuit of less highlights that this effect can cloud our judgement about the opportunities in our life. When deciding what is essential and what is non essential, we tend to overvalue the activities we already partake in. McKeown recommends Zero based budgeting can be used for personal decision making.
Marie Kondo tidying up missing
How do Cognitive Dissonance and Loss Aversion play into this?