Oh man, what a wonderful thing to consider. I would do so much.
For starters, I would spend MUCH more time with my wife and five kids. They are all under the age of 6, and these years are just so important. It makes me sad to have to be away at all, not to mention the 40-50 hour minimum workweek in the US. So, that would be my primary. Spending time loving on them, exploring, teaching, bonding, etc.
Secondly, I would pursue my passion for outreach with people who, like myself, struggle with self-harm and self-injuring behaviors. I actually just launched a second Steemit account @nssi-advocate to hopefully do that when I can. I'm not a licensed counselor or anything, but I think I have a valuable story to add that may help others find healing in their own lives. I would love to be able to dive into that without having to worry about money.
Third, I would hone my hobbies! I have been a self-taught woodworker for the past 6 years and have loved learning new skills and making interesting projects. But, with the five kids and full-time job, I rarely get time to create. Between that and my dream to build a custom bicycle, I would love to have more room on the margins to explore my self-care interests.