Buddhists very often discuss the difficulty, if not impossibility, of achieving enlightenment in one lifetime. Well, doesn't even asking this question assume that this is your first lifetime? Doesn't this go against what the buddha taught, as well as the whole concept of samsara? To quote good old wikipedia...
http://en.wikipedia.org/wiki/Saṃsāra_(Buddhism)"According to the Buddha, the beginning point of Saṃsāra is not evident, just as there is no beginning point to a circle."
"All beings have been suffering in Saṃsāra for an unimaginable period, and they continue to do so until the attainment of Nirvana."
From the Pali Canon
"From an inconstruable (sic) beginning comes transmigration."
He then goes on to state that there is more water in the tears an individual has shed in all of his lifetimes than there is the water in all of the oceans. So, to put it mildly, each of us has been here many, many times.
That being said, according to the buddha, this is by no means our first lifetime. So, if you reach enlightenment in this lifetime, you WON'T have done it in one lifetime. The buddha is clear about this. Yet discussions about the length of time required to reach enlightenment run rampant. For all you know, you've been on this mission to achieve enlightenment for millions of lifetimes. Don't sell yourself short, as if you're starting from nothing.
Comments
the very fact we seek enlightenment is a blessing.
I'm in Samsara, my parents have been in Samsara, their parents before them, my great great great great grand-parents, in short all beings not properly awakened have been in Samsara since beginningless time. Checkmate. Now, if you were to wake up, you wouldn't be in Samsara anymore.