Don’t loose belief in your capacity

The length of your period of dullness is also no sufficient reason for losing belief in your capacity or your spiritual destiny. I believe that alternations of bright and dark periods are almost a universal experience of yogis, and the exceptions are very rare. If one inquires into the reasons of this phenomenon,—very unpleasant to our impatient human nature,—it will be found, I think, that they are in the main two. The first is that the human consciousness either cannot bear a constant descent of the Light or Power or Ananda, or cannot at once receive and absorb it; it needs periods of assimilation; but this assimilation goes on behind the veil of the surface consciousness; the experience or the realisation that has descended retires behind the veil and leaves this outer or surface consciousness to lie fallow and become ready for a new descent. In the more developed stages of the yoga these dark or dull periods become shorter, less trying as well as uplifted by the sense of the greater consciousness which, though not acting for immediate progress, yet remains and sustains the outer nature. The second cause is some resistance, something in the human nature that has not felt the former descent, is not ready, is perhaps unwilling to change,—often it is some strong habitual formation of the mind or the vital or some temporary inertia of the physical consciousness and not exactly a part of the nature,—and this, whether showing or concealing itself, thrusts up the obstacle. If one can detect the cause in oneself, acknowledge it, see its workings and call down the Power for its removal, then the periods of obscurity can be greatly shortened and their acuity becomes less. But in any case the Divine Power is working always behind and one day, perhaps when one least expects it, the obstacle breaks, the clouds vanish and there is again the light and the sunshine. The best thing in these cases is, if one can manage it, not to fret, not to despond, but to insist quietly and keep oneself open, spread to the Light and waiting in faith for it to come; that I have found shortens these ordeals. Afterwards, when the obstacle disappears, one finds that a great progress has been made and that the consciousness is far more capable of receiving and retaining than before. There is a return for all the trials and ordeals of the spiritual life.

Ref : Letters on Yoga Vol. III