After experiencing a state of spiritual enlightenment (that ah ha moment when you are in complete alignment with all that is, when you suddenly have a glimpse of the true meaning of life, when you are in complete present moment awareness and “see the light,” experience an awakening...), that can be induced through drugs, chanting, trauma, near-death experience, meditation, birth, a manic episode, sex, yoga, or even spontaneously...Well, then comes the part of the process where we must digest, we must integrate into our daily lives, into our relationships all that we've discovered or experienced during our enlightened state.
Thich Nhat Hanh sums this up beautifully when he says, “before enlightenment, chop wood and carry water. After enlightenment, chop wood and carry water.” I think he says this because after we experience a state of enlightenment, our natural inclination is to want to repeat the means in order to continuously achieve the ends, but then life still carries on as usual... So, if you had your enlightened state of mind through meditation, your natural inclination will be to want to meditate all the time to maintain that enlightened state, or if the enlightened state of mind was achieved when smoking marijuana, the natural inclination will be to want to smoke marijuana all the time to maintain that state. But, seeing as we live in the physical world, where we all have responsibilities, we cannot be meditating all day, or smoking marijuana all day, well, some of us can, but not the average person, and then even if we could, we'd end up suffering because of our attachment to it...
And so we can begin to make it a daily practice to awaken, to stay awake, as we experienced in our enlightened state, so that over time, each part of our day, each moment of our day, we can begin to fully feel alive to the true meaning and purpose of what it is we're living for (love, God, service, peace, joy, gratitude), and living fully in the present moment with all of our spiritual truths... And so this is why we maintain a spiritual practice even after we've experienced an enlightened state... because we forget, we must integrate, and we can always get higher in light, love, and awareness ;)
So, what is a spiritual practice? Exactly what is sounds like, an act you consciously choose to do that connects you to your spiritual Self, connects you to others, connects you to the Divine/Universe/God (much more on this topic of spiritual practice later).