It's "okay" to keep using windows 10 for a while. Once security updates stop, you don't immediately get attacked because usually bad actors take some time to find out new exploits. When the OS was being patched, updates would come out at close to the same rate as the exploits became known. That way, threats were limited. Now that security updates stopped, the OS will become riskier and riskier to use over the years.

And although it's a risk for everybody using it, it's not the same level of risk for every individual. Odds are you aren't a political or public figure, so it's not like hackers will actively target you, specifically. Just mind that leaving sensitive stuff on your computer might not be the best idea from now on. And even on the internet, although Browsers have their own security features, they rely on the OS as well for security, so even if you try and put your data on the cloud, it's not a guarantee.

The thing is that now most developers will phase out updates for a "dead" OS, so you might get stuck with older versions of professional programs and drivers that too will not have new security patches and so. The biggest threat will be if you connect through the internet via public networks or download a lot of stuff from the internet, particularly if you sail the high seas.

It's not a death sentence and your computer won't self combust (take for example the many factories still relying to Windows XP for their software), but keep in mind that especially things on the internet will become increasingly riskier, so consider not saving your passwords and banking info in this computer.