What does nothing can hold you back mean?

If you stumble, do not waste a moment's thought over it—remember the lesson, and say—

I must be up and doing. That is past and gone, and it will not hold me back.

Just go about your Father's business each day, accomplishing the tasks that are yours—each day, doing the little things, bright-eyed, clear-visioned and with a cheerful countenance, seeing the stones and ruts in your path, but able to see how to step over or around them because the Light within your heart has become the light of your world, combining love and wisdom.

Every positive stand you take builds character, increases your strength, lifts you out of your negative state, gives you the power to conquer your weaknesses and tends to make promptness, courage, resolution and trust, habits, which will replace the negative habit of making excuses. Truly, nothing can hold you back unless you hold to it.