Holla Kaye ,
They are two cause that we became lazy .
1. Lack of interest : If you dont have an interest on that particular thing you will easily became lazy but you can deal on it by motivating yourself like thinking what benifits can you will get on that particular thing.
2. Enviroment: The enviroment also is one of a cause of laziness ,for example your room, you feel not comfortable and you easily became lazy in studying in your room ,theirs a solution on that just rearrange or redesign your room.

Hope that tips help you