Desire is the only reason for doing anything.

Why get out of bed in the morning? Because I want to.

Why eat breakfast? Because I want to.

Why work on losing weight? For health? For appearance? Why do I want
those things? Because I do.

Why be nice to the person in front of me? So they'll think I'm nice?
Why do I want that? Long or short, it comes down to because I want to.