Guess its name

Hello
You're no stranger to me
You follow me around
You bring me up
You drop me down
You spin me round and round
I can't see the ground
When you've got me up high
And I can't see the sun
When you've got me down low
You keep me off balance
Always pushing me to the extreme
Bipolar is your name
You'll never leave me be
I'm the company you love to keep