If it's your ultimate goal to be better at throwing things out, and not just to have less stuff short-term, you're actually punishing yourself for engaging in the desired behavior when you withhold credit for doing so (or spend any time on negative feelings as a result of doing the task), which seems counterproductive.

You might find an auxiliary habit of patting yourself on the back (or similar small reward-feeling behavior) when you do your task to be more helpful!