When professional organizers work with people to help them declutter and get organized, a very common practice is to keep a box nearby in which to put things that will be donated to charity. The problem is that once the job is done, the now decluttered customers tend to think that there is no longer a need for a charity box. They think the charity box is a tool used only while decluttering with a professional organizer. But it isn't. It is one of the best tools for staying decluttered in the long term after the professional organizer has left. In short, every household needs to have a charity box.
Now, allow me to digress just a little bit with a story...
When I was going to BYU, it fascinated me that every dorm laundry room on campus had what was called a D.I. box. (D.I. is short for Desert Industries, which is the Latter-day-Saint-run second-hand thrift store.) When students wanted to get rid of perfectly good clothing, they could put it in the D.I. box, and every so often, the box's contents were taken to D.I., donated to charity. I made use of that box, and I came to consider it a convenience.
When I got married and established my own household, I found that I still needed something to store items that I intended to take to charity. It would be silly to make a trip just to donate one thing, so I began using a cardboard box as the D.I. box for our family. When it got full, then it was time to make the trip to donate it. I kept it in the garage so that when it was full, it was very convenient to just put it in the car trunk. (And then I put "Donate stuff to charity" on my list of errands.)
Keeping a charity box in your garage will do several things for you. 1) You can get an immediate lift by removing clutter from your living space, with a set place to put it. 2) It will help you become reconciled to letting go of things by giving you time to discover you don't miss it. 3) It institutionalizes charitable giving in your home, which builds the character trait of generosity little by little.
If you want to remain decluttered over the long term, keep a charity box around and add things to it from time to time when you find they aren't being used.