Based on what I know of Imposter Syndrome and the Dunning-Kruger effect, it seems you’re at your most competent when you feel like you’re at your least.

I’m not sure how you come to that conclusion, even with the internet meme version of the Dunning-Kruger effect. In the meme version, the incompetent think they are most competent, but I don’t think it follows that the most competent would think they are least competent.

I would summarize the actual Dunning-Kruger effect as: people tend to think they are a bit above average, and actual skill factors in only slightly. Worth emphasizing that these results are over groups of people, and individuals have extreme variation.

https://en.wikipedia.org/wiki/Dunning–Kruger_effect

For anyone wondering, this doesn’t actually work, because the bananas will realize they are upside-down.

There are over 2 million animal species on Earth, and one species is responsible for 99.9% of all lethal attacks. Ban Humans (from existing)!

This is known as the Chino’s Paradox

If there isn’t a clear “yes, let’s do it at this time” it’s always a no.

This is also worth understanding in case someone asks you out. If they invite you to some undesirable activity (e.g. a sport you are not interested in) with just the two of you, then declining will be taken as a more general lack of romantic interest. (Disclaimer: asking you to an activity alone is not 100% sign of romantic interest).

This will often be followed by a significant change in behavior towards you (e.g. less joking / flirting). This is not them being angry or trying to get back at you. They are trying to respect your lack of romantic interest, and possibly handling their own emotions of rejection, disappointment, and such. If you do lack romantic interest, this is mostly unavoidable; people will always be sad when the person they like doesn’t like them back.

If you do have romantic interest, then try to suggest alternative activities and be extremely blunt that you do want to date them. Make sure you have a concrete day you will do something together, even if you don’t figure out exactly what it is. If you can’t even settle on a day, set a date on when you’ll talk next about a date.

This dilemma is why flirting is so complicated. Basically two people are trying to slowly build confidence that they like each other, while maintaining total deniability about it. I know this sounds challenging, but it’s much harder in practice.

For this reason, Azzu’s suggestions are absolutely correct.

Expanding on “be graceful when rejected” – make sure you are prepared for a “no” answer. One small help here is an alternative activity planned for yourself, so that you have something to look forward to either way.