That being said, the days can run long (and you will easily work 60 hours per week without batting an eye) but you will almost always look forward to going to work.
There is a lot of sitting. You have to train yourself to get up and move around every so often.
Every animation studio has a different pipeline. Be prepared to make adjustments as needed.
Get away from the computer when not working. This will prolong your career and keep your hands in good shape.
Enjoy the challenges that come with each new scene and you will always have a smile on your face.
For 3D animation, it is definitely longer and more time consuming but once you learn some animation techniques, it becomes easier. Soon you realize many techniques are reused in different medium, film, TV shows, YouTube etc. As a 3D animator, you can lead down a path on how to code and perform new techniques even. 3D animation usually means more people and more time involved. Many 3D animated TV shows takes months of development and movies take years, so keep that in mind.