After my knee accident I understood how important it is to stay physically active and never allow the age-related physical disability creep in.
Few days ago I realised: same applies to mental abilities. In school we were forced to develop ourselves and now it's so easy to simply stop this and always do what one did yesterday.
And now I realised an even more important thing: the same applies to the emotional health!
Being all on your own and feeling hopeless when you're old does not depend on whether you find a life partner, have children, or earn enough money. It, sadly, or maybe luckily, depends on only you, and your disciplined effort to stay on the surface. Once you start drowning in any of those 3 areas, with age, it will become less and less possible to break out of it. And I say it again, marriage and family does not prevent it!
I look at a homeless person and think: this could be me. Not because I'm unlucky or didn't find a boyfriend. No. It's because today I let this negative thought grow in my mind. Because yesterday I was lazy and skipped the gym. Because one more day at work I didn't actually read the documentation but brute forced the solution. It all adds up. Every single negative self thought, every time I give up on something. Every time I choose comfort over curiosity.
The most important thought of this year, perhaps.