I had a working mapreduce job that was 300 lines of fairly high level java code. Compact, terse, expressive, everything you don't see in most Java. I came back over a the weekend and my boss/coworker made it 'configurable' which means he added 800 lines of code.

I fucking cried.

He was like, "I hoisted out some stuff that should have been behind interfaces." ... I didn't need an interface because I only had ONE and specifically made the API have a low surface area so this could occur IF IT NEEDED TO.

I sucked it up and took it in stride.

Jumping in and solving a problem is usually the last thing you want to do, but that character trait(flaw) is what people think of as a good leader. Someone who will take you over a cliff with conviction.