There is irony in that metaphor, because it is taught that enlightenment (a.k.a. Buddha nature), is within each of us at all times. We all have the potential to wake-up (Buddha means "one who has awakened") and stay awake, but for most it is a long, slow process. Yet, as the Buddha said, drop by drop the bucket is filled. Moment by moment we are slowly building our awareness. We are more fully awake.
Yoga teaches that all phenomena, although apparently seperate, are on the deepest level, part of one whole. Like cells in the body maintaining their individual identity, we are behooved and more whole once we recognize the oneness of all life. Just like life is simultaneously fragmented into the many and just one whole, realizing that is complex but in practice is simpler then it seems.
To realize enlightenment, we have to follow the Way, a lifestyle dedicated to conditioning enlightenment. The Way for each person is different, so each person much navigate by their heart-center. It can take years of yoga practice before polishing the mirror enough to begin to clearly hear the heart-center. Once there it becomes simpler, but just takes time. Slowly the challenges keep polishing the mirror, we are asked to let go of so much we never knew we were holding on to. All past hang-ups, guilts, judgments, insecurities, attachments and all of the ego is called up in front of us, we have to find the skillful way to naturally resolve and disolve each and every one. And slowly, day by day we are more awake, more present.
Being mindful, as fully as possible. Listen totally to the heart. Be absolute love and compassion for all in all ways. Surrender to reality. Then just keep it up, in the face of ALL challenges, in EVERY single moment. Let the ego dissolve and die. Empty out everything that is not the essential self, just allowing it to leave in its own time. Then, you are there. No control, no rushing, it has to happen in its own time. For most, its much slower then a snail crawls. Watch seeds germinate, or grass grow. It's slower still.
Are you up for the challenge? It's rewards are immense and better than any amount of money. All of the worldly goals happen along the way, but no object or power can compare with being one with All That Is.
In day-to-day practice it is so easy to other think it. Presence is much simpler then that- don't argue with the mind-chatter, just be the "silent witness" watching all vibrations (mental, physical, internal + external). But it still comes down to patience and persistence, because we can't escape our karma. Keep sowing positive seeds every moment and just witness yourself awakening into the cosmic mind.
Drop by drop, we awaken.
Practice all day, everyday, and it will happen!