Lao Tse, currently spelled Laozi, according to Wikipedia, said, “The journey of a thousand miles begins with a single step.”
What he didn’t say is that that single step can set off profound changes. Imagine kicking a pebble with that first step and starting a rock slide. Not that all change is bad. (Except on my computer; software update has crashed it twice today.) Sometimes that first step seems to be into an elevator heading for the sky.
Fitness can be a profound change. We may not recognize ourselves. We may find that the strength we have gained in our bodies has changed our power in the world. Other people may treat us differently, in both good and less good ways.
We can react to that with fear, ice cream, and blankets, or we can gird up for adventure. I vote for adventure.