Both good and bad karmas are bound.
The humans bind karma. If they cause harm or misery to people, they go to the animal form. If their karmas give happiness to others then they return to the human life or go to the celestial level. So the life level depends on the type of karma bound. Once the level is decided, one has to go through that level, experience the effects and return to the human form.
To understand the Science of Karma, please visit here: https://www.dadabhagwan.org/path-to-happiness/spiritual-science/the-science-of-karma/good-and-bad-karma-only-in-human-life/