Recall the 'simile of the raft'. In case you don't know it, you can find it
here. The analogy is given of the Buddha's teaching being a raft used to cross to the other shore, that other shore being a metaphor for Nirvāṇa. But on reaching the other shore, goes the instruction, what do you do with the raft? Carry it with you?
'How useful this raft has been to me! For it was in dependence on this raft that, making an effort with my hands & feet, I have crossed over to safety on the further shore. Why don't I, having hoisted it on my head or carrying it on my back, go wherever I like?' What do you think, monks: Would the man, in doing that, be doing what should be done with the raft?"
"No, lord."
"And what should the man do in order to be doing what should be done with the raft? There is the case where the man, having crossed over, would think, 'How useful this raft has been to me! For it was in dependence on this raft that, making an effort with my hands & feet, I have crossed over to safety on the further shore. Why don't I, having dragged it on dry land or sinking it in the water, go wherever I like?' In doing this, he would be doing what should be done with the raft. In the same way, monks, I have taught the Dhamma compared to a raft, for the purpose of crossing over, not for the purpose of holding onto. Understanding the Dhamma as taught compared to a raft, you should let go even of Dhammas, to say nothing of non-Dhammas."
This is where Buddhism diverges from many other religions, who make their scriptures - the Bible, say - into an absolute truth in itself. But just because dhamma should be 'let go of', this is so only when the river is crossed; if you 'forget the whole thing', or not make use of the raft, without having crossed the river, then you're still bound to Saṃsāra. So the advice is - make use of the opportunity when in a situation where you can benefit from it because the chance may not come again for a long time.