I think this quotation means that a habit is too weak to be felt that we don't even notice that we were already developing it and then we'll just realize that we can't take it away because it is too strong to be broken. A simple explanation.

            This quotation is really true. I already proved it to myself. When I was only but a little child, I used to bit my fingernails, and as I grew up, that 'used to', became a 'habit'. A habit that I can't take, and sooner, because of that, my mother is always scolding me because she said, biting fingernails is a bad habit, or what-so-you-called 'malas'. Up to now, I'm still doing that, that's why I do have ugly fingernails.

            Agh, that's sucks.....

                This mathematical equation- like quotation for a success in life was said by Albert Einstein.

                It means in order for you to success in life, you must have to first, Work. Of course, you should work hard for you to be able reach your goals/dreams. Second is, you must Play. Play means Rest. It means you should not give all your time and effort in your work or to take it too seriously, you must give yourself a time to rest, relax, and enjoy, and give yourself a reward you think you deserve after the hard work you've done. Then last is to keep your mouth shut, means you should not be a 'Gossip Queen'. You should learn or you should be a good individual for yourself and a good company for others.

                Example, a person wants to be successful. He won't be successful if he will be lazy, opportunities comes from those who seek on it, he also can't be successful if he's only working and working and working and not getting any rest because his health might give up. So what's the use of his hardworking, right? And if a person has many enemies because he can't keep hi mouth shut, he will not be successful.

                Albert Einstein is really a genius! He applied a mathematical equation in our daily life.

      
        It means that your number one worst enemy is no other than you, yourself, your own conscience, and of course our dear God who's with us everyday. No matter how great you lie to others, yourself knows the truth. No matter where you try to go, you will find you. You know you better than anyone do and can do. You know every inch of you.

       For example, an amateur killer (I daresay an amateur because professional killers already have no conscience that's why killing for them is easy to do) killed. He professionally hid all the evidences against him or of what he did. And yes! He escaped from our laws, but whatever he'll do, he's conscience knows what had happened. For example, he will hear voices everywhere, and see unusual things, and it he end, he will be insane.
 
      That's it, the killer killed and no one knows it except for himself and his conscience ate his dear sanity.

       A very sad story, indeed!