When can one say that one has truly entered the spiritual path?
“The first sign (it is not the same for everybody) but in a chronological order, I believe, is that everything else appears to you absolutely without importance. Your entire life, all your activities, all your movements continue, if circumstances so arrange things, but they all seem to you utterly unimportant, this is no longer the meaning of your existence. I believe this is the first sign.
There may be another; for example, the feeling that everything is different, of living differently, of a light in the mind which was not there before, of a peace in the heart which was not there before. That does make a change; but the positive change usually comes later, very rarely does it come at first except in a flash at the time of conversion when one has decided to take up the spiritual life. Sometimes, it begins like a great illumination, a deep joy enters into you; but generally, afterwards this goes into the background, for there are too many imperfections still persisting in you…. It is not disgust, it is not contempt, but everything appears to you so uninteresting that it is truly not worth the trouble of attending to it. For instance, when you are in the midst of certain physical conditions, pleasant or unpleasant (the two extremes meet), you say to yourself, “It was so important to me, all that? But it has no importance at all!” You have the impression that you have truly turned over to the other side.
Some imagine that the sign of spiritual life is the capacity to sit in a corner and meditate! That is a very, very common idea. I do not want to be severe, but most people who make much of their capacity for meditation—I do not think they meditate even for one minute out of one hour. Those who meditate truly never speak about it; for them it is quite a natural thing. When it has become a natural thing, without any glory about it, you may begin to tell yourself that you are making progress. Those who talk about it and think that this gives them a superiority over other human beings, you may be sure, are most of the time in a state of complete inertia.”
[CWM2, 4:103-104]

How can we find the Divine who is hidden in us?

…the first thing is to want it, and know precisely that this comes first, before all other things, that this is the important thing. That is the first condition; all the rest may come later, this is the essential condition. You see, if once in a while, from time to time, when you have nothing to do and all goes well and you are unoccupied, suddenly you tell yourself, “Ah, I would like so much to find the Divine!”—well, this—it may take a hundred thousand years, in this way.
 But if it is the important thing, the only thing that matters, and if everything else comes afterwards, and you want nothing but this, then—this is the first condition. You must first establish this, later we may speak of what follows. First this, that all the rest does not count, that only this counts, that one is ready to give up everything to have this, that it is the only thing of importance in life. Then one puts oneself in the condition of being able to take a step forward.
[CWM2, 6:342]

Why should I take up the spiritual path?  Is it for a personal gain, even if it is high and spiritual?  Is it for serving the society and humanity?  Is it for the sake of the Divine?  But then what does Sri Aurobindo mean when he says even personal liberation, perfection, fullness must not be pursued for their own sake but for the sake of the Divine?

It means that all this perfection which we are going to acquire is not for a personal and selfish end, it is in order to be able to manifest the Divine, it is put at the service of the Divine. We do not pursue this development with a selfish intention of personal perfection; we pursue it because the divine Work has to be accomplished.

But why do we do this divine Work? Is it to make ourselves…

No, not at all! It is because that’s the divine Will. It is not at all for a personal reason, it must not be that. It is because it’s the divine Will and it’s the divine Work.

No personal desire should come in

So long as a personal aspiration or desire, a selfish will, get mingled in it, it always creates a mixture and is not exactly an expression of the divine Will. The only thing which must count is the Divine, His Will, His manifestation, His expression. One is here for that, one is that, and nothing else. And so long as there is a feeling of self, of the ego, the person, which enters, well, this proves that one is not yet what one ought to be, that’s all. I don’t say that this can be done overnight but still this indeed is the truth.
It is just because even in this field, the spiritual field, there are far too many people (I could say even the majority of those who take to the spiritual life and do yoga), far too many of these who do it for personal reasons, all kinds of personal reasons: some because they are disgusted with life, others because they are unhappy, others still because they want to know more, others because they want to become spiritually great, others because they want to learn things which they may be able to teach others; indeed there are a thousand personal reasons for taking up yoga.

One single motive—the Divine

But the simple fact of giving oneself to the Divine so that the Divine takes you and makes of you what He wills, and this in all its purity and constancy, well, there are not many who do that and yet this indeed is the truth; and with this one goes straight to the goal and never risks making mistakes. But all the other motives are always mixed, tainted with ego; and naturally they can lead you here and there, very far from the goal also.
But that kind of feeling that you have only one single reason for existence, one single goal, one single motive, the entire, perfect, complete consecration to the Divine to the point of not being able to distinguish yourself from Him any longer, to be Himself entirely, completely, totally without any personal reaction intervening, this is the ideal attitude; and besides, it is the only one which makes it possible for you to go forward in life and in the work, absolutely protected from everything and protected from yourself which is of all dangers the greatest for you—there is no greater danger than the self (I take “self” in the sense of an egoistic self).
[CWM2, 7:189-90]