Who am I?

Question : Who Am I?

"I am your constant companion. I am your greatest helper or heaviest burden. I will push you onward or drag you down to failure. I am completely at your command. Half the things you do might just as well be turned over to me, and I will be able to do them quickly and correctly. I am easily managed – you must merely 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 all 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 work with all the precision of a machine plus the intelligence of a human being. You may run me for profit or 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?"

Answer : I am Habit