"I can creep up on you in an instant and change your mood.

I can lift you up. I can drag you down.

I have the ability to make you doubt yourself.

I can cause you to cry.

I can give you a boost of energy or I can discourage you.

I am so powerful I can create in you a great purpose

But, often I will point out all the reasons why you will fail.

I am such a big part of you that you just go about your day taking me for granted.

This is not good - not good at all, because I can do so much for you,

If you would just let me.

But, know – I am at your beck and call

My job is to follow not lead.

I always give what you request.

What Am I?"