At the software engineer level, I see two big things that affect morale negatively. The first is legacy code-- you may occasionally be beckoned into a haunted house. Prepare to remember words and software versions you haven't seen in 5-7 years. That sucks, but it's going away as fast as we can kill it. Second is shifting product priorities. As we work to remediate technical debt, we also have to respond to market imperatives. Every team has had their priorities turned on a dime at one time or another. It can be frustrating, but we all understand, and most people here are buoyant enough not to let it bring them down. The new priority is usually interesting in its own way.