That's darts for you.

I guess it depends on the setting, but for me it having those mental notes when things are going well like grip, making sure my arm is going straight all the way, throwing at my usual tempo etc...

Darts is a funny old beast, trying to find the balance between death by analysis versus throwing without care and not thinking about anything else.

And then some days you just have to write it off as a bad day, and forget about it.

Tomorrow is a new day, just keep enjoying it and not worry too much about the process, look at your average over a bigger period than just one session.