Answer:
The higher I climb, the hotter I engage. I cannot escape from my crystal cage.
You saw me where I never was and where I could not be. And yet within that very place, my face you often see.
You use a knife to slice my head. And weep beside me when I am dead.
I'm not man's best friend, I'm their enemy, I can mark your end, yet you do not see me, I am very small, but very tough, If you have me, then you have it rough.
When young, I am sweet in the sun. When middle-aged, I make you gay. When old, I am valued more than ever.
What do angels sing in the shower?
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?