I think "Hope"(dream) would be a beautiful solution, too!
I am a tree on highest mountain.
Something far away we are trying to reach.
I am many, don't try countin'.
There are many people hoping for something and maybe everyone has many "trees" he is looking at. But there is no point counting them.
I grow skinny. I grow fat.
Hope can have all different shapes and it can change over time. You sometimes change your mind and thus change hope to some point.
Chop me down and I'll grow back.
Reminds me of someone trying to destroy your dreams but hope is returning. They say 'hope' is what dies last.
Many mountains are my home.
Many people can have the same dream or hope for something.
You don't plant me. I just grow.
You cannot control what you want. Sometimes you desire forbidden things.
Sometimes I just go away. Though people wish that I would stay.
Sometimes an opportunity vanishes and as a result, hope dies eventually even though you still want to pursue it.