One should never assume that it's impossible to slow down, or that by doing so, someone is going to shame you for it. Learning to stay focused isn't going to lead you to less work, but it will certainly help you to manage stress, allow you to do more, and generally provide a smoother working experience.
You are definitely more than just a job title. Focus on the aspects of who you are that you like the most and seek to fulfill them on a daily basis. You'll feel better about yourself and your situation, and maybe you'll even develop a healthier perspective about your identity than you had when you were working full time.