I think the answer is practice, for a few reasons. One is obvious: conversation is a skill. Just like a novice chess player can spend 5 seconds figuring out which squares the knight can move to while an intermediate player spots a fork to force trading a strong bishop or exposing an overworked queen, exposure to similar situations rewires your brain to work faster in those situations.

Another reason, though, is to me one of the main benefits of social interaction in the first place: The brain rewiring also makes you think about what other people would think, want to hear, say to you, etc, even when they're not around. That sure can give you better answers in conversations, but more importantly, I think this is just genuinely a nice way for the brain to be. In the same way that dogs are happy playing fetch, humans are happy living with other people in mind. Maybe because it feels like not everything is your responsibility, or that you worry less about what you should be doing, or that you look forward to laughing about disasters later... I'm not entirely sure. Whatever it is, it's nicer than the alternative.

I may suggest to answer genuinely about how you are instead of "how is life" — yes, my life is hard because of many ongoing family health issues, but I might still be OK in the moment. Or sleepy from a bad night of sleep, or hungry because I skipped breakfast. Or happy because I got my favourite parking spot. Or had a nice meal....

Say "I'm about to have coffee, so that's good :-) "

Alternately, instead of trying to prepare for every possible answer, you can constrain the possible replies significantly by being the one who asks the question in the first place. "How's your day going?" is only ever going to get some variation of "good" or "bad". You only need to respond with "great to hear that", or "sorrt to hear that, hope it improves soon". That's it.