After 7 years of intense, INTENSE, dedicated, sustained, systematic meditation, the Buddha sat one night, resolving never to rise until he had attained his goal. He relays it as follows (Vinaya Patika 111.4) :
"I roused unflinching determination, focused my attention, made my body calm and motionless and my mind concentrated and one-pointed.
Standing apart from all selfish urges and all states of mind harmful to spiritual progress, I entered my first meditative state, where the mind, though not quite free from divided and diffuse thought, experiences lasting joy.
By putting an end to divided and diffuse thought, with my mind stilled in one-pointed absorption, I entered the second meditative state quite free from any wave of thought and experienced the lasting joy of the unitive state.
As that joy became more intense and pure, I entered the third meditative state, becoming conscious in the very depths of the unconscious. Even my body was flooded with that joy of which the nobles say, 'They live in abiding joy who have stilled the mind and are fully awake.'
Then, going beyond the duality of pleasure and pain and the whole field of memory-making forces in the mind, I dwelt at last in the fourth meditative state, utterly beyond the reach of thought, in that realm of complete purity which can be reached only through detachment and contemplation.
This was my first succesfull breaking forth, like a chick breaking out of it's shell..."
Even to reach the first of the four dhyanas mentioned requires years of incredible effort, and, it is said, thousands of previous lifetimes. At least a dozen people are said to have reached enlightenment over the next few decades of the Buddha's life.