I know its basically impossible to actually alter someone wlses memory through Magick, but what about changing your own memory? Say i was stuck somewhere i didnt want to be for hours on end, and time moved miserably slow. What if i could alter my memory of the event so that time seemed to move very fast? Theoretically, this really changes nothing, except i wouldnt have the lingering boredome of being there forever. I would feel surprised and glad time seemed to movw so fast after changing the memory of it. Another thing could be, in the future you could use this as a sort of one-way-pseudo-time-travel by taking a huge chunk of memory away.
Eh, well it is possible to "alter" the memory of someone through suggestion. This is common in court cases with children and survivors. Their memory of the entire event could be changed by the police or lawyer suggesting things to them.
False memories are a well-known issue with determining the veracity of recalling past events.
I don't see why you would want to change a memory about waiting too long somewhere. It is in the past; it no longer affects you as more than a memory. And knowing how long of a wait it was can possibly help with future planning.
As for actually traumatic events, my opinion becomes a bit fuzzy. On the one hand, using suggestion to repress the memory of a terrible event may be helpful to some, but it also has a tendency of being dredged at the worst times in people's lives. Actual counseling and learning to cope and recover become more important in the long run.