I found the hardest thing to initially get my head around was going home at the end of the day wondering what I'd achieved.

Moving from tangible daily outputs (code etc), to longer term feedback loops can be just as rewarding, you just need to step back slightly.

Empowering others to achieve their potential, watching them grow. Watching great products evolve. Understanding and directly influencing tech decisions. Being able to look further than the next sprint. Interfacing with external parties, seeing how they approach similar / new problem spaces.

IMO, this never gets boring.