Formal:
* Profitez pleinement de la vie. (This is the most literal translation and is quite formal.)
* Vivez votre vie à fond. (This means "Live your life to the fullest" and is a bit more informal than the first option.)
Informal:
* Profite bien de la vie! (This is a more casual way to say it, and is more suitable for friends and family.)
* Vis ta vie à fond! (This is the informal version of "Vivez votre vie à fond." )
* Savoure chaque instant. (This means "Savor every moment" and is a beautiful way to express the sentiment.)
The best way to choose the right phrase depends on the context and the person you are speaking to.