I also struggled with the same question for years until I realized that I'm already doing my purpose which is helping people feel & live a healthy, happy and abundant richer life. I truly believe prosperity is our birthright. Reading books like The Power Of Now, Dynamic Laws of Prosperity by Catherine Ponder, Think and Grow Rich, my favorite Secrets of the Millionaire Mind, graduating my Millionaire Mind Intensive and enrolling myself in personal growth live courses gave me much clarity. I also journal and do my hour of power inspired by Tony Robbins almost everyday (working on doing every day). I'm a work in progress so as you.
You are here for a good purpose.
Now I realized my purpose is to create wealth and abundance so I can help and give more. Since I desire to give $100,000 a year to help people and the environment, this means I must make ten times of this per year. It takes a bigger person and character to make this happen...this is my challenge.
I hope you also realize your purpose.