Sri Aurobindo
Letters of Sri Aurobindo
Volume I - Part 4
As for the doubts of which you have written, I cannot write much today for obvious reasons and in any case writing is not the remedy, though it may help and encourage – for these doubts rise not from the intellect but from the vital mind which sees things 
according to its condition and mood and needs something else than what the mind asks for to satisfy it. It is perfectly true that these reasonings have no force when the vital is in its true poise of love or joy or active and creative power, and when the vital is depressed then it is hard and seems sometimes impossible, so long as the depression is there, to surmount the trouble. But still the clouds do not last for ever – and even one has a certain power in the mind to shorten the period of these clouds, to reject and dissipate them and not to allow them to remain until they disappear in the course of nature.
By all means use the method of japa and bhakti. I have never insisted on your using the method of dry or hard tapasya – it was some idea or feeling in your own mind that made you lay so much stress on it. There are some to whom it is natural and necessary for a time, but each ought to move in his own way and there is no one rule for all – even if the objective is and must be the same, contact and union and opening to the Divine.
In the end these doubts and depressions and despairs must cease. Where the call of the soul perseveres, the response of the Divine must come.
Na hi kalyāṇakṛt kaścid durgatiṃ tāta gacchati.1