At 40 we've only just begun.
In 2014 aged 38, I stepped out of corporate and ever since have been making my own way. It's tough (everyone says that) and certainly not what I thought it would be. But I realised that, at 38, I wasn't even half-way through my working life and a few years invested finding a way to work that worked for me for the second half would be an investment well made. On that theme, this is a great video shared by Gary Vaynerchuk:
If you have the desire, go do it (and my advise if you want it is focus on your first 3 years of cash-flow). If you don't, no worries, what you're doing is amazing too.