"Realization is not something that is learned from a book. It is a gift, given to us by the Lord, something valuable that we can never forget. Krishna gives us this gift through difficulties. He puts us in situations where we find ourselves struggling against circumstances or our own weaknesses so that we understand that He is the Supreme Controller. Sometimes we may find certain situations re-occuring in our lives. Perhaps you keep causing misunderstanding in your relationships because you talk without thinking when angry. Or it can be some other problem that keeps coming back. At that time, we have to kneel down before the Lord and beg Him, "Please Krishna, help me to overcome this weakness. Help me to understand the lesson you want to teach me" And then, when we realize, the problem may automatically go away.
But Krishna knows what is best for us. Perhaps the removal of a certain weakness, may fill our heart with pride. "I dont lose my temper anymore. Nobody is more calmer than me. I have conquered my biggest weakness." This pride may be more damaging to our spiritual progress than that weakness itself. So Krishna will not remove it - and He will let us struggle, because the more we struggle, the more we remember Him, and the more closer to Him we shall go.
Difficult people and difficult situations are sent by Krishna to help us grow towards Him."
(From a lecture by H.G GaurSunder Prabhu in Pune. Its not the exact words, but whatever I remember I felt like sharing here)