When you can't stop thinking about someone, it usually means that you have strong feelings for that person. These feelings could be positive or negative, depending on the nature of your relationship with them.
If you have romantic feelings for someone and can't stop thinking about them, it could mean that you are infatuated with them or have developed a crush. You may find yourself daydreaming about being with them, imagining scenarios where you two are together, or constantly checking their social media profiles. These thoughts and feelings are common when you are attracted to someone and are a natural part of the human experience.
On the other hand, if you can't stop thinking about someone who has hurt you or caused you pain, it could be a sign that you are still processing your emotions and need to work through your feelings. You may find yourself replaying past interactions or conversations with that person, trying to make sense of what happened and why.
In either case, it's important to recognize that thoughts and feelings are a natural part of the human experience and that it's okay to have them. However, if you find that your thoughts are interfering with your daily life or causing you distress, it may be helpful to talk to a therapist or mental health professional who can help you work through your emotions and develop coping strategies.