A/N: Usual disclaimers apply. This one's a bit shorter than the rest, but don't let that deter you from reading it anyway.
habseligkeiten - (n.) few, paltry belongings one finds special, whose values evolve from personal meanings and from happiness and sentiment of having these certain objects [german]
Childhood is generally a time of happiness, where one begins to find who they are, how they fit into the world, and how the world itself works. Even as humans adjust and grow, they still come back to the little things that shaped who they are. It could be a favored toy, a favored book, a favored place to sit and watch the world go by. While other things are cast aside, these few remain, in defiance of the ever-changing world.
For Hermione Granger, it was her well-used copy of the Oxford English Dictionary. The very first book she had ever tried to read, and eventually the first one she read cover to cover. These many years later, the book had needed a rebinding, as well as a couple of strong charms to ensure the pages wouldn't get any more damaged. Though new editions came out with some frequency, Hermione kept this first book separate from the others, less as a reference, and more to remind her of where she started. Without this book, Hermione Granger would be a totally different person.
For Neville Longbottom, it was an old trowel. It had a couple of charms on it, mostly to keep the tool from rusting or falling into serious disrepair, but was other wise unspectacular to most. In fact, it was not even one Neville used much anymore, as he had tested and perfected some of his own specifically to deal with magical plants. However, it held a place of pride behind Neville's desk, because it was the first one he had ever held, and the only one that the Longbottom family had documented proof that he and his father had used together. That wizarding photograph sat next to the trowel, and Neville often looked to it when he had a tough decision to make. For as much as he wished that he had been able to talk with his father when growing up outside of St Mungo's, he knew that with his father's influence, Neville Longbottom would have been an Auror, like his father before him, instead of Neville Longbottom, proud owner of the most exotic and successful greenhouse in Britain.
For Harry Potter, there was very little from his time in the Dursley household that he wished to hold onto. When Number 4 went on the market, Harry bought the house, had it dismantled, and sold off the land for someone else to develop. No one else would live in that building, and no one except those closest to Harry would get to see what one piece of it he salvaged for himself. From inside the cupboard under the stairs, there was one piece of wood that a young Harry had taken a dull knife to and carved "Harry's Room." It was the only bit of Number 4 that he had not personally witnessed the destruction of, and it would forever serve as his reminder of the consequences of letting evil grow too powerful in the world. He would strongly prefer to live in a world where such a thing had not been necessary, but of all people, Harry Potter knew the danger of allowing the innocent to be forgotten.