Your stuff is a compass
Your stuff is a compass, and it guides you to places within yourself that needs ACCEPTANCE, HEALING, SUPPORT, COMPASSION, & FORGIVENESS.
Once you reconcile with yourself, it's easier for you to look at an object and be like: "Ok, this is what it is", as opposed to: "This is what it represents".
Example 1 : For instance, an old concert ticket stub is not taking up too much space, but it was from a show that you saw with your ex., therefore, it might be taking up residence in your mind, so it might be time to let it go.
Example 2: Clothes might be sentimental, but do you actually have the space to keep said items? What is the likelihood that you will ever use the item? If both answers are yes, you get to keep it.
SUGGESTION: Take a photo of it or journaling about why it was special to you before your part away.
REMEMBER: Bringing something to a consignment shop or donation doesn't have to be sad, think about how the piece will make someone else feel.