As far as I know, Force meditation should be performed in a calm fashion. As Wookipeedia states:
By meditating, Force-sensitives could reach a deeper state of relaxation, making them easier to connect with the Force with a clear mind.
Even powerful Jedi master Qui-Gon Jinn is meditating during a "stand-off" period while lasers separates them.
Why is Rey meditating in the middle of a lightsaber duel? And why is Kylo waiting patiently for her to gather strength, instead of pulling his lightsaber back and attacking her repeatedly from other side while she meditates? That whole scene was so surreal for me... Rey was like "Oh! The Force!" and she kind of doze off for a while, and Kylo is just looking at her in anger.