I am most perplexed about this aspect of the training as it is explained by Mahasi Sayadaw in Manual of Insight.
He writes about path-oriented and fruition-oriented maturing of insight knowledges;
If, on the other hand, one practices insight with the goal of attaining a higher path [i.e., path-oriented insight], then the course of one’s insight knowledge will be different from this fruition-oriented insight. This is because the path-oriented insight must fulfill the four functions of right effort. So it may not be as easy to develop higher insight knowledges during path-oriented insight as it was during fruition-oriented insight. That is why the Mahāṭīkā states, “The course of fruition-oriented insight is different from that of path-oriented insight.”
Explaining that in order to enter previous fruition one ought to make the resolve;
If a noble one wishes to become absorbed in the attainment of fruition, he or she should determine a time limit for the attainment in advance by resolving, “May the fruition attainment persist for such and such a period of time.”
Whereas if one wants to practice for higher path one resolves otherwise;
you should practice with the purpose of attaining higher paths and fruitions. To do this, you should first determine how many days you are going to practice, and then resolve: “May the fruition that I have already attained no longer arise during this period of time; may the next higher path knowledge and fruition knowledge arise instead.”
He also adds that it can be very frustrating if one resolves on higher path and is therefore unable to return to the prior fruition;
Otherwise if you resolve, “From now on, may the next higher path knowledge and fruition knowledge arise,” you may find it difficult to return to the previous fruition. Then the meditator may feel upset if he or she can neither gain a higher path knowledge and fruition knowledge nor return to one previously attained. [...] You may remain in that condition for a long time, anywhere from one or two days to months or years.
If the determination for higher path was made and one finds it difficult to return to previous fruition, is it then just a matter of making new resolves or is one somehow stuck developing the path for a while?