basically there's this M. Ward song called To Go Home and it has this verse:
"God, it's great to be alive
takes the skin right off my hide
to think I'll have to give it all up someday"
This world is filled with so many wonders and so many beautiful and terrible things...Just to think I'd never feel the warmth of the sun or hear or see laughter.
For me, A hundred lifetimes would not suffice to grow tired an weary of this world. But I know these are words backed by good health, loving friends and family and a more or less stable economic position.
The thing is, when people are suicidal, none of these things matter, and no on can truly help. My mom is a psychologists and has told me about anonymous patients who were had been making progress and were by all symptoms stable and happy only to take their lives after the worst had passed and were doing well again.
If someone wants to kill themselves, short of interning that person, there's nothing we can truly do, every word of encouragement and every kind gesture will be like a stab in their hearts.

Be kind, be loving, respect life and acknowledge every person you meet as a human being that affects your life.
Another good reason to live is the never-ending possibility of being grateful.