I appreciate everyone's advice regarding your job, but as others have alluded, I suggest the bigger point is to go deeper into your values.
It sounds like your job is tightly-coupled with how you see yourself, so perhaps consider things outside of your job (volunteering, extra-curriculars, investing, etc.) that are closer to what you value.
One way to handle getting through these low periods is to shift your mindset of your job being a reflection of what you like and more your job enabling you do, participate what you like.
Personally, being of service of others, using my vacation days to help others, and investing in projects and people I believe in has helped offset some of the feelings you may be feeling.
It sounds like your job is tightly-coupled with how you see yourself, so perhaps consider things outside of your job (volunteering, extra-curriculars, investing, etc.) that are closer to what you value.
One way to handle getting through these low periods is to shift your mindset of your job being a reflection of what you like and more your job enabling you do, participate what you like.
Personally, being of service of others, using my vacation days to help others, and investing in projects and people I believe in has helped offset some of the feelings you may be feeling.