Play an exciting game. Record it as you play it. Watch the recording.
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The narcistic approach, but hey, I like it!
Seriously though, there's also a bit of benefit to doing so, as it's WAY easier to spot your mistakes while just casually viewing what you've done, vs being in the heat of the battle. One of the things I notice a lot when proofing my vids for editing errors before uploading them is the items I miss. It's so easy to get tunnel vision heading to an objective marker, but revisiting a playthrough via watching your capture shows all the things you didn't see, and they literally stick out like a sore thumb!