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😅 I am going to go for the latter!

I think it's fine just as it is - "I'm used to thinking about how I used to think." You are used to reminiscing. Whether you think the same way now or not, is not implied by the sentence.

'I'm used to thinking about how I used to think, but I think differently now.' Implies a change.

Aha! lol Thanks. It's funny, we all talk a certain way, but then when I have to write, sometimes I'll stare at my sentence for minutes, wondering if it's grammatically correct.