Life's challenges. What are they? Getting to your goals. Surpassing expectations. Getting to a place where it is civil living.
Life is being disappointed, sadden by everything. Realizing with one good thing that comes your way another thing brings it down and crushes it. Life is teaching you that even if you get to that thing that makes you happy it'll just bring you back down again. Depress you. Make you cry. Yeah, life is cruel. It hurts. Some of us are luckier than others. Worked harder than others to realize that life is going to kill us. One way or another it is going to kill us.