It means that the progress itself is much faster if one forgets oneself, including the will for personal progress, and gives oneself completely as an instrument to the Divine for His Work.
If one reads the full prayer as below it becomes evident enough.
January 10, 1917
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Dost Thou then want to teach me that every effort that has my own being as its aim will be useless and vain? That action alone which has as its motive the radiating of Thy Grace is accomplished with ease and success. When the will acts in the external life, it is powerful and effective; when it attempts to practise going inwards, it is without force or effect…. So all action undertaken for personal progress becomes more and more unfruitful, and consequently rarer and rarer. On the other hand, all outer action seems to gain in effectivity what the inner has lost. Thus, O Lord, Thou takest the instrument as it is, and if it has to be refined, that will come in the course of the work.’
Affectionately,
Alok Da
