I'm the perfect example of the quote above. I dreamed of writing from childhood through adolescence and being a young adult. Then I kept dreaming about it as I raised my children and supported my husband in his career. Finally, in my early fifties, I leaped headfirst into the deep waters of the writing world.
I'd reached a frustrating time in my life, living in a community new to us, children grown and on their own, no job, no friends. I struggled mightily until I saw an opportunity to begin writing, to try my hand at that long-desired activity. An advertisement in a magazine was the spark I needed.
Step 1: I did a little research on the correspondence course school that promised to teach me how to write for children.
Step 2: I enrolled and began a course that took 18 months. No email in those days for me so the lessons and letters went by snail mail. By the time I'd finished the 10 Lessons in the course, I was hooked for life.
Step 3: I read every book I could find at the local library about the craft of writing.
Step 4: I joined a small critique group in our community
Step 5: I worked up the courage to begin submitting to children's magazines
Step 6: I leaned how to accept rejection and move on to the next project immediately.
Step 7: I subscribed to newsletters and magazines for writers and joined a writers association
Step 8: I felt like a writer when that first sale occurred
All that began just over twenty years ago. I've never regretted taking that first step, nor following with all the rest. I have been incredibly fortunate to be published in many places. When a door opened, I didn't hesitate, I ran straight through. These twenty-plus years later, I'm a whole lot older but my enthusiasm is no less, my ability has grown, and I look forward to continuing to be a writer for many more years. As long as mind and body keep going, so shall this writer.
I wrote an article quite some time ago about writers who didn't start writing until after the age of fifty. Each interview I did brought new insight to the reasons people waited so long and also gave me inspiration and motivation to continue my own writing. You can read the article here.
Whether it's writing or something else you've not tried in your life, you can do it. Take that first step like I did and you'll feel renewed and eager to sprint forward as fast as you can. Those over fifty have to make good use of the years left to them.