On peut toujours ce qu’on veut, pourvu qu’on le veuille bien.

We do what we have to so we can do what we want to.

"If you can't you must, and if you must
you can"..

Sometimes things become possible if we want them bad enough.

If you do the things you need to do when you need to do them, then someday you can do the things you want do when you want to do them.

Il faut exiger de chacun ce que chacun peut donner

Quando gli dei vogliono punirci, avverano i nostri desideri.

We cannot always do what is best, but we can do what is practical at the time.

We can but try.

Dilige et quod vis fac. (Love and then what you will, do.)

If you can’t, you must. If you must, you can.

It is not enough that we do our best; sometimes we must do what is required.

Must is not the same as can, Lyra'.
'But if you must and you can, then there's no excuse!

If you can't do what you want, do what you can.