This hits the nail on the head with me too. After experiencing a good session, it is easy to expect the same or better next time.
This morning I remember feeling slightly dissapointed because I felt anxious during the relaxation period. I expected to feel better.
This can be the case in much of life. Even to the extent that doing something well can almost be 'worse', because there is that to live up to next time.
My expectation can go in cycles, from having a great burden of expectation to having very little.
For me, it seems to boil down to acceptance of the here and now, which is something that I am learning with the help of NSR.