“I admire your willpower.”
You offer a coworker some cookies that you made. She says no because she's on a diet. You are impressed, because you usually can't say no to sweets. This is how you compliment her.
I admire your willpower.
When you "admire" a person, you are impressed with them and wish that you had the same qualities. "Admire" can be followed by a person's name or title:
The person I admire most is my mother.
Or, you can "admire" a certain quality of a person:
I admire my mother's generosity.
"Admire" is usually used in the simple present tense. You say "I admire ___", not "I am admiring ___". There is one situation where you use "am admiring". That is when you are looking at something that a person owns or has made. If you look at it for a long time because you think it's great, you can say:
I was just admiring your DVD collection. You have some nice ones here.
"Willpower" is the ability to control yourself. If you "have strong willpower", you are able to stick to your long-term plans, and not follow your moment-by-moment desires.
People usually think of willpower in connection with avoiding actions that are bad for us, but hard to resist. These include over-eating, spending money, and having sex with people that you shouldn't.