I grew up with a ridiculous amount of stuff. But somewhere in grad school, I began wonder why do I have all this stuff if I am not using it? -- especially when I was about to move across the country again. Long story short, it was a process but I have found minimalism unexpectedly freeing.
A hard item for me to let go of is books. If I had kept every book I was given, acquired, or bought, I would have well over 3,000 -- and these are all books that I like, mind you, not throw-aways! In the end, I kept the books I knew I would want to reread every few years and a few reference books. Despite the fact that books are my life, I have pared them down to under a hundred. (Yes, it is possible.)