If you can design perfect circuits that always work when first built then you are an amazing engineer.
Me, not so much. Simulation has caught many problems (some quite subtle) in my circuits before I built them that were not obvious from looking at them (such as an op amp that had diode protection across its inputs which caused a problem when I used them in a window circuit).
So I never build a circuit without simulating it first. I'm not that keen on troubleshooting and modifying circuits after they are built. :wink: