Also, you must understand, that finding the purpose can be a cumbersome and long-lasting process, that even can take months or years to nail perfectly. And you should be ready for adjusting it over time.
And, we’re not discussing your personal WHY, which is a similar but slightly different approach. I’ve taken Simon Sinek’s online course on this in order to teach others how to do it, but it’s not in scope for this blog post.
This process has turned out to work in 9 of 10 cases, but might still need adjustment to fit your context.