Have you ever done something you really didn't like or that you weren't 100% convinced of? There's nothing worse than working with a divided mind.
What do I mean?
When you're doing something and your mind is not entirely "into" the activity your actions become unfocused and you scatter precious energy, not to mention time.
"Now and then discouragement is due to just one cause - letting the mind run on one thing while you are doing another."
Source: http://www.welt.de/english-news
At such time you are a house divided against it-self and you are falling. You are a stream of energy running in two channels instead of one, and you are therefore too weakened to accomplish anything on either channel. And you feel weak and discouraged.
You are practicing mental scatteredness, which is the way not to live. You are living in the death part of your consciousness and your body is actually disintegrating while you are doing it. You are letting go your life, your individuality.
You are letting your desire and your will, which are all one force and the only one, spread out all over creation. You are allowing yourself to be pulled to pieces by conflicting centers of attraction outside you. You have become the puppet of environment for the time being.