For example, I previously tended to use a bottom-up approach to development. However, SICP showed me the benefits of what it calls "wishful thinking" with a more top-down approach.

It also helped me finally 'get' functional programming. Even in situations where other programming paradigms make more sense, I'll still opt for a functional style a lot of the time and avoid state.

I'm also a lot more confident with higher-order functions and closures after SICP help me understand them better. Seeing how cons pairs can be implemented as functions was simply mind-blowing. I think being able to use some of these techniques have improved the way I code.

There are a lot of other topics, such as the meta-circular evaluator, that I haven't had the opportunity to put into practice, but are nonetheless absolutely fascinating.