I have generally enjoyed celebrating birthdays, although the worst day of my life fell on one. Now, they tell me that I have a fatal condition to plan for, and that I shall have to keep working harder to stay alive. However, I have learned not to beat myself up too much about not having achieved certain things yet by diverting to others I have, and/or to noting that I'm making significant progress toward my goals, which is better in some ways. Whenever I do knock something off my to-do list, I have to find another goal anyway.
Stock-taking can also be done monthly, seasonally, and on the new year, as well as upon completion of projects, semesters, and relationships. If you are suffering from comparison to the usual milestones of life, you might try intentional eccentricity. For instance, if you can't afford new furniture, you may be able to live even better by scrounging with a sense of style.