True contemplation is the work of a love that transcends all satisfaction and all experience to rest in the night of pure and naked faith. This faith brings us close to God that it may be said to touch and grasp Him as He is, though in darkness. And the effect of that contact is often a deep peace that overflows into the lower faculties of the soul and thus constitutes an "experience." Yet that experience or feeling of peace always remains an accident of contemplation, so that the absence of this "sense" does not mean that our contact with God has ceased.
To become attached to the "experience" of peace is to threaten the true and essential and vital union of our soul with God above sense and experience in the darkness of a pure and perfect love.
And so, although this sense of peace may be a sign that we are united to God it is still only a sign --- an accident. The substance of the union may be had without any such sense, and sometimes when we have no feeling of peace or of God's presence He is more truly present to us than he has ever been before. If we attach too much importance to these acccidentals we will run the risk of losing what is essential, which is the perfect acceptance of God's will, whatever our feelings happen to be.
But if I think the most important thing in life is a feeling of interior peace I will be all the more disturbed when I notice I do not have it. And sense I cannot directly produce the feeling in myself whenever I want to, the disturbance will increase with the failure of my efforts. Finally I will lose my patience by refusing to accept this situation which I cannot control and so I will lose the one important reality, union with the will of God, without which true peace is completely impossible.
Seeds of Contemplation by Thomas Merton