"30 or 40-year-old is a child when considering the potential of human existence" Unknown
When we consider our potential to learn, our potential to experience and our potential to exist, we have to remember all the brilliant people of history and the modern-day.
Every amazing thing that you have ever heard someone do, was performed by someone 95% the same as you (1)
The main things that separate us are the experiences we have and the way we choose to perceive them. This metric can literally be experimented with till the day you pass and there is no need to slow down. The experiences will change in nature, they may be less physical but there is so much still available to explore.
Think of the amazement of our brain, with each neuron having up to 1000 connections to each other (synapses), sending information around the brain at up to 268 mph, with a total of around 86 billion neurons, meaning there are over 100 trillion synapses (connections between neurons) working in synchronicity all day, every day.
And yet we still feel the need to think "I don't have time" or "I started too late" or "I'm just not that kind of person"
Look in the mirror, appreciate that image, and remember that you are a child when considering the potential that you still have left to experience.