Fuerza de voluntad power will

[ROBINDESBOIS]

How can I use power will in this sentence:
No voy al gimnasio todos los días porque no tengo mucha fuerza de voluntad.
I don´t go to the gym every day because I have not enough power will. ??????

[Rusty]

It's 'will power'.

I don't go to the gym every day because I don't have enough will power.