"What doesn't kill you", refers to facing a challenge that is beyond your comfort zone. So to go through an experience which is hard and sometimes painful. The reason why is it is hard or painful is because you are being forced to change. Resistance to change is where your pain comes from. The more one resists adapting to changing circumstances, the more pain one experiences. Pain is actually the symptom of the heat of transformation, or adaptation, of something changing in your system, whether this is physical, emotional or intellectual, all are aspects of who you are and is represented by 'personality'. So pain is good, because it means you are healing, or changing some aspect of who you are. When you go through something hard like this, then after you are finished with it, you have let go of something old and now have something new. This is why it is good, because now you are more updated, refreshed and new in some way that you weren't before. You are better able to survive the more you allow the old ways or things to go, and adapt to what is new. The universe and world is constantly changing, every micro second, the more you learn to face what is here now and respond to it,, the more you also will become like the universe, spiritual, flowing and adaptive. That's our challenge, to learn how to welcome change and be one with it.