Habits - Do you serve them or do they serve you?

I am your constant companion.
I am your greatest asset or your heaviest burden.
I will push you up to success or down to disappointment.
I am at your command.
Half the things you do might just as well be turned over to me
for I can do them quickly, correctly and profitably.
I am easily managed, just be firm with me.
Those who are great, I have made great.
Those who are failures, I have made failures.
I am not a machine though I work with the precision of a machine and the intelligence of a person.
You can run me for profit or you can run me for ruin.
Show me how you want it done.
Educate me.
Train me.
Lead me.
Reward me.
And I will then...do it automatically.
I am your servant.
Who am I?
I am a Habit.

Author Unknown