There are different ways to forget things. One way is to learn something new. This will take your attention away from the other thing you are trying to forget. This will eventually cause your brain to store the new information rather than the old information.
Another way to forget something is by putting it in our memory for a long time until you get bored of it. As time goes on, it will get pushed out of your mind without having any negative consequences.
The third way is by forgetting the feeling that you get when thinking about it. As we grow older, we learn to inhibit our emotions which would help us focus on the current time and place. Doing this can lead us to forget what caused that emotional response in the first place.
The last way is by forgetting how it felt when you originally learned it. We pick up new information all of the time but only a small fraction of it is stored in our long-term memory. Most of it will just be forgotten unless you bring it up again.
Of course there are many more ways to forget things but these are the four main ones. A combination of these four can help people forget information quickly and for good. Sometimes people cannot deal with the emotional side effects of forgetting something. To them, they would rather just learn how to forget things by learning new information.
So this is how to forget something.