Who Am I?

I am your constant companion

I am your greatest helper or your heaviest burden.
I will push you onward or drag you down to failure.
I am completely at your command.

Half of the things you do you might as well turn over to me and I will do them
 - quickly and correctly.

I am easily managed - you must be firm with me.
Show me exactly how you want something done and after a few lessons
I will do it automatically. 

I am the servant of great people
and alas, of all failures as well.
Those who are great, I have made great
Those who are failures, I have made failures.

I am not a machine though I do work
with the precision of a machine
plus the intelligence of a person.

You may run me for profit or run me for ruin
it makes no difference to me.

Take me, train me, be firm with me, and
I will place the world at your feet.

Be easy with me and I will destroy you. 

Who am I?

I am Habit

Side note:  During yesterday's broadcast of the Arnold Palmer Invitational (Tiger won dramatically on the 72nd hole) they discussed Tiger Woods' daily regimen.  Starting at 6:00am daily with 90 minutes of weight lifting and ending at 6pm after almost 10 hours of practice.  Name anothe player on tour that works that hard - and this is perhaps the best play of all time.  Hmm . . . I wonder how he got that way?