You will notice when the Spirit has sparked a fire within you. Do everything you can to protect that light and warmth. Far too often we let down our guard, allowing the world and the Evil One to pull us back from God and all that is eternal toward that which is temporary and meaningless.
"The seed of life has been planted - guard it with everything you have. Otherwise you have nothing to which you can apply your labors, and nothing with which to carry them. You have received the Spirit - do not extinguish it. If you are zealous, be zealous for what is great. Watch over what has been given you, what you have acquired. This acquisition is the coin which will buy you the treasure. If it is lost, all is lost. Armies at war take all care to secure their positions. It is the same here."
- St. Theophan the Recluse. "Rules for the Beginner of an Ascetic Labor." The Path to Salvation: A Manual of Spiritual Transformation, translated from the Russian by Fr. Seraphim Rose, (Arizona: The Holy Monastery of St. Paisius, 2006), p. 219.