The Deeper Meaning of Refuge

What is meant by going for refuge is that you are seeking refuge from some fear. All the objects [Buddha, lama, guru, etc.] in front of you are what is known as the causal refuge, because they serve as the cause for bringing about the resultant refuge within you. You should entrust yourself to these objects from the depth of your heart, and you should see the objects as protectors. The resultant state of your own future realizations, becoming an arya being and attaining buddhahood--which depends on your own actualization of the path--is called the resultant refuge. Someone in difficulty seeking the assistance of a high official is analogous to someone seeking refuge in the causal refuge.
But depending upon others' protection forever is not a courageous way of life; therefore, one has to try to achieve a state where one is no longer dependent upon such a refuge, and this is likened to taking refuge in the resultant buddha, dharma, and sangha. That is the process of taking refuge by a person of high faculty and courage. This practice should be done not for the sake of oneself alone but rather for the sake of all other sentient beings. When you cultivate such an aspiration focused toward the achievement of the omniscient state, it is very much like the generation of the bodhichitta mind.
--from The Union of Bliss and Emptiness: Teachings on the Practice of Guru Yoga by the Dalai Lama, translated by Thupten Jinpa