I would say that decluttering is a very large part of selling your home. It is always best to have someone with you that is not emotionally attached to any of your things. I also think that when going through your stuff, you should put things in different categories. Such as saving for the new house, items to donation and items to trash. If you’re buying things for the new house, use what you don’t need to stage your current home. I tell my clients to think of this as a vacation. You are going to an Air B&B, so pack your suitcase, and put everything else in storage.
This can be a stressful time, but try to have family and friends help you. I recommend having someone outside of the home as a task manager so you don’t get stressed out with each other. They can encourage you to get things in order and excited about your new home.