Try to diversify your interests and engage in more real-world activities. That way, you won't be so fixated on the fictional character. Also, think about the flaws of the character to break the idealized image in your mind.
One way could be to remind yourself that they're not real and engage in hobbies or socializing in the real world. That might reduce the simping. Also, limit your exposure to the fictional content related to those characters.
Well, one way could be to set limits on how much time you spend thinking about them. Another is to consciously focus on your own goals and the real people around you. Remember, fictional characters can be fun but shouldn't take over your thoughts too much.
It could be that the character's story and development have really resonated with you on an emotional level. Maybe they represent something you aspire to or find comforting. Also, the way they are depicted, their looks, or their personality might have captured your interest strongly.
Try to focus on their flaws and negative traits. Maybe that'll make you less attached.
Try to focus on real-life relationships and experiences. That might shift your attention away from the fictional one.
Diversify your interests. Engage in new hobbies or activities that take your mind off the fictional character. Also, think about the flaws or unrealistic aspects of having a crush on someone who isn't real.
One way to stop is to remind yourself that the character is fictional and not real. Also, limit your exposure to content related to them. For example, don't constantly re-read or re-watch the material featuring the character. Instead, explore new things and expand your interests.
Try to focus on real-life activities and hobbies. It can help shift your attention away from the fictional world.
Try to focus on real-life relationships and activities. Meeting new people and getting involved in hobbies can shift your attention away from fictional characters.
You could try thinking about different things, like your goals or plans for the future. And give yourself some time; eventually, your mind might naturally move on from the fictional character.