There are two types of nostalgia , restorative and reflective, according to Svetlana Boym, author of The Future of Nostalgia . Restorative nostalgia inspires you to go back and change or recreate your past, while reflective nostalgia allows you to accept your memories for what they are. People can experience both types of nostalgia, but restorative nostalgia is more likely to make you feel sad, Boym writes. For example, maybe fall always makes you think about going to football games with your terrible ex. Or perhaps visiting your college reminds you of all the stupid antics you got into when you were drunk. Basically, if you remember how you felt or acted during a difficult time in your life, you might not have the most positive memories, even if they are technically considered "nostalgic."