The remebrance of a good time or event that makes you happy.
remembring the past.

One of the best feelings you could ever feel. Nostalgia can take you back to a time that had a much different flow than your current lifestyle. You may be an adult right now and feel nostalgic of the days you would play outside in a little sandbox when you were 5 years old. It makes you go "Ahhh... the good old days." Or it doesn't have to be a throwback of that long. Maybe you have had work piling on your table for 3 weeks and you finally finished it. You'd think to yourself. "Wow... this is so nostalgic. I can party with my friends and have a normal sleep schedule now." Nostalgia is warm and brings a smile to your face.

A bittersweet longing for things, persons, or situations of the past.
The condition of being homesick; homesickness.

Playing Halo 3 in 2017, knowing it has been 10 years since it came out. Enough said.

A remembrance of something that was important to you, something that you loved, something you heard as a infant or a toddler, something that is unforgettable.

reminiscent of a time when the world ceased to move around you because you had it all.