Dreams of Reliving the Past.
 

How seriously should we take dreams of reliving a momentary past experience

Entertaining.

Depends on the message but they're often shown to represent something you're currently going through or have yet to heal or resolve. Your current life situation(s) might be similar or the effect, even in a roundabout sort of way, of that past event. It could be that how you act and respond to situations today, stem from that event. So in other words, I would take them seriously. They're being shown to you for a reason. If you don't understand why, then ask and answers will come.

I agree with Yaoughta

There is a lesson in it.
There may be many lessons in it.

It depends on a few things, most notably the feelings surrounding that experience, both in the dream scape and in physical reality.

So, what is the feeling experienced when reliving that experience?

When you say 'momentary', do you mean, as in a quickly passing situation?
Or do you mean that although it was 'momentary' as in perhaps it was somewhat significant (or even very significant), but it was momentary whatever it was.

If it is indeed the latter, then it most likely means that there are issues around that topic that you are holding on to, or at leads need some attending to. It doesn't have to necessarily be negative - it could simply be your inner guidance trying to get you to move in a certain direction that you may not have done up until the present moment.

~pmk