fickle
Changing feelings or choices a lot for no good reason.
Fickle means changing your mind or feelings frequently and unpredictably, especially about things you're supposed to care about or stay loyal to. A fickle person might be your best friend one week, then ignore you the next, then want to be close again the following week, all without any real reason for the changes.
The word often describes loyalty or affections that shift like the wind. Someone with fickle taste in music might obsess over one band, then suddenly declare them boring and move on to something completely different. A fickle fan might cheer wildly for a team when they're winning but abandon them the moment they start losing.
Weather can be fickle too: a fickle spring day might be sunny and warm in the morning, cold and rainy by afternoon, then clear again by evening. Fortune and luck are often called fickle because they change without warning or fairness.
The word carries a negative feeling. Being fickle suggests unreliability and shallowness. While it's normal to change your mind sometimes as you learn and grow, fickleness means changing constantly for no good reason, making it hard for others to trust or depend on you.