You said it yourself, to "add value to his/her life". Ergo, you have an innate value system. The ultimate source of this system is God.
One instinctively knows right from wrong, and that people will consciously act against their own best interests, (smoking, drunkenness, reckless driving, etc.), is proof of what is called "original sin". This is utterly simplistic, I know.
Most all believers are taught that suicide is a non-forgivable sin; as you may not confess, can't be contrite in denouncing the act, and you're unable to be penitent.
We accept suffering because we know within ourselves, if maybe only subconsciously, we possess original sin, and within ourselves, have accepted values to atone for it.