Everyone should have their own memorabilia box. It is up to you how small or large it should be but it should hold the things that mean the most to you. The note that you could read over and over and it still has the same effect on you as the day you received it.
A memorabilia box tells the story of your life. It holds notes from the loves of your life and the part of your life that is now a faded memory. It holds ticket stubs from memorable concerts, reunions, special birthday cards and most importantly for me, letters from my children. Reading a card my daughter wrote to me when she was twelve means more to me today, now that she is leaving for college in a few weeks.
Make the box accessible so you can keep putting things that are meaningful to YOU in the box.
As a professional organizer I am always helping people decide what to keep and what to let go. There is a difference between getting rid of things you no longer use and that are not important to you and a box full of the memories of the life you have lived. You may not go into that box very often but you know in your heart that if you need it, it is there.