For me, not using a debugger is kind of like not using valgrind. If you stop operating on memory directly, you forget you ever needed valgrind. Likewise, if you write functions instead of methods, then you can just take the problematic input, and evaluate your function on it, and inspect the output - without needing to get the whole program into the right state for stepping through.

I kind of gave up on step-through right around the same time I started writing multithreaded code as well.