This one is fun. I think of it as self-caricaturing. Not trying to come up with a "straw man" exactly, but rather a comical/cynical oversimplification that still kinda fits. The goal is to compress it as much as possible while still having it be as accurate as possible. The more you can compress without losing much/the less nuances you lose, the more this self caricature tells you about yourself.
For example, I sometimes joke that I'm a redneck that doesn't want to believe he's a closeted hippie. It's a quite lossy caricature, obviously, but every time I do something consistent with that caricature it gives me an opportunity to examine whether I'm merely doing the cached self thing or whether I can find the underlying heuristic (and notice whether it's any good).
Another neat use is to signal that you're self aware. People will try to fit you into their caricatures, and if you can lampshade this, they'll perk up and listen for how you don't fit this caricature. After all, if that's exactly what you were, how could you be aware of how it looks and laughing about it?
One good way to ensure that your plans are robust is to strawman yourself. Look at your plan in the most critical, contemptuous light possible and come up with the obvious uncharitable insulting argument for why you will fail.
In many cases, the obvious uncharitable insulting argument will still be fundamentally correct.
If it is, your plan probably needs work. This technique seems to work not because it taps into some secret vault of wisdom (after all, making fun of things is easy), but because it is an elegant way to shift yourself into a critical mindset.
For instance, I recently came up with a complex plan to achieve one of my goals. Then I strawmanned myself; the strawman version of why this plan would fail was simply "large and complicated plans don't work." I thought about that for a moment, concluded "yep, large and complicated plans don't work," and came up with a simple, elegant plan to achieve the same ends.
You may ask "why didn't you just come up with a simple, elegant plan in the first place?" The answer is that elegance is hard. It's easier to add on special case after special case, not realizing how much complexity debt you've added. Strawmanning yourself is one way to safeguard against this risk, as well as many others.