The sign for that's-life is also used for "tough luck" and tends to be shown by spelling the letters TL while throwing the hand forward (sort of like throwing it in the face of the person to whom you are signing.) The "L" ends up with the palm at about a 45 degree angle (by that I mean that the palm is facing halfway down, halfway forward).
You will also see this concept (that's life) expressed by showing the sign THAT and then the sign LIVE/LIFE.
Notes: