It is very difficult to understand much less have the insight to see what Sir Paul said about the pleasure and its reverse or inversion but it is absolutely true. This is why in the Gita, Krishna told Arjuna about being balance in duality. It is a special trick used by advanced ascetics which prevents them from being gutted by the reverse of a pleasure or by the converse of a pain.
The problem with the whole thing is that when the pleasure or pain is overwhelming, when it is more than the individual can contain, the person cannot make a decision to be balanced, no more than a small yacht can keep itself afloat in a violent sea storm.