Changing your personality to suit the person you're interested in is a behavior that some people engage in for various reasons. While I can't provide a definitive answer to why you specifically do this without more information, I can offer some common underlying factors that may contribute to this behavior:
Desire for Acceptance: Wanting to be liked and accepted is a natural human need. When you're attracted to someone, you might feel an increased desire to be appealing to them, which can lead to altering your personality to match their preferences.
Fear of Rejection: Fear of rejection can drive people to modify their behavior to avoid disapproval. You may worry that if you show your true self, the person you like might not find you attractive, leading you to adopt a persona you believe will be more appealing.
Insecurity: Low self-esteem or insecurity about your true personality may lead you to think that the "real you" isn't good enough for the person you're interested in. Consequently, you may try to emulate traits you think they would find more attractive.
Lack of Self-Awareness: Sometimes, people are not fully aware of their authentic selves or haven't explored their true preferences and values. As a result, they may mimic others to fit in or gain approval.
Past Experiences: Past rejections or experiences of not being accepted as yourself might lead you to believe that changing your personality is necessary for romantic success.
Idealization: When you have strong feelings for someone, it's easy to idealize them and put them on a pedestal. In this state, you might try to be what you think they want rather than being yourself.
It's important to remember that healthy and meaningful relationships are built on authenticity and mutual understanding. Changing yourself to please someone else is not sustainable in the long run and can lead to feelings of emptiness or dissatisfaction.
Embracing your genuine self and finding someone who appreciates and values you for who you truly are will result in more fulfilling connections. If you catch yourself repeatedly changing your personality to match others, it might be helpful to work on building self-confidence and self-awareness. Learning to accept and love yourself will ultimately attract people who appreciate you for the real you. If you find that this pattern persists and causes distress, talking to a therapist or counselor can provide valuable insights and support in navigating your emotions and relationships.