De-cluttering gives you the space you also need for things you actually use and need. Feel free to use big plastic chests for storing your junk, even moving boxes. Just properly label everything. Sort the things as you go through them, especially those you think still have some market value in garage sales (fyi, even old magazines and books sell pretty fast).
If you can afford to be a little more OC, list the things you put in a chest or box and tape it outside for easy reference.
If you commit to doing this twice a year, or once at least, your mountain of