Lessons:

One of my managers emphasized balancing growing the team (long term success) and delivering (short term success). With one particular project, we planned out what was needed to help the junior engineers grow. To support them in this, I took on some of the grunt work. At one point, my plate was clear, so I thought "I'll lay the groundwork for this other engineer". I hadn't noticed how drained I was and how addicting the recharge was from this bit of greenfield development. I quickly completed the project. Unfortunately, the other engineer was mad. That was the one piece of work they were most looking forward to.