Сложноватенькие:
I can't swim - I didn't do it before even once.
I can't love her - she is too silly..
I can't do my homework by myself, because it's too difficult for me.
I can't be a king - I only dream about it..
I can't decide my degree - I like either drawing or singing..
Легкие:
I can't sing.
I can't read.
I can't hear.
I can't be happy.
I can't do it.