The sky will not fall, and your PC won't stop working. Your email will still be delivered, you can still browse the web and your games will not disappear overnight.
Are you still running Windows XP?
.... you are almost alone.
In spite of what you may have heard or imagined, Windows XP is not running slowly because Microsoft have ceased supporting it, if your PC is slow it's for the same reasons it has always slowed down in the past, multiple unnecessary files hidden away that can be easily removed, the registry is probably bloated with now irrelevant entries, your hard disk is probably full of fragmented files and being the age it is, the hard drive quite possibly has faulty sectors or perhaps it is nearing capacity, and of course you may have picked up a bit of Malware along the way. All this can still be repaired, but what cannot be repaired?
The most immediate task for you is to stop using Internet Explorer and move up to Firefox, until May 2018 security updates will continue to be provided, but it is an older version than on later Windows versions. Microsoft refuses to allow the new versions of IE to be installed on XP. The good news is that Firefox is better than your version of IE, and is fully patched and up to date, sadly Chrome is no longer up to date and will never be updated, it is still better than IE, but not for long.
There are no more updates, so turn off Windows Update, as a by-product you won't get nagged by Micro$oft to upgrade.
If you are running Microsoft Security Essentials, stop it!! Download the free Avast Antivirus and if you want a greater level of protection then pay the small asking price to get additional protection - much better than anything Microsoft ever offered. Virus definitions and updates stopped long ago for Microsoft Security.
Now the bigger problem.......
When your printer dies and you want another, read the box before you buy it to ensure it comes with drivers for XP. Over the coming months hardware will become available that no longer supports your operating system, this could be a printer, scanner, camera, video import dongle, anything at all, even hardware for the inside of your PC may not be useable on what is now considered to be an aging system. Worse still, some software installations no longer support XP. For instance, if you require an up-to-date installation of iTunes to manage or maintain your iPod, iPad or iPhone, then it is time to upgrade from XP.
Windows XP will continue to function as long as you want it, and I will be available to fix it for as long as you want me to. You should be aware that there are flaws in your operating system that may make it vulnerable to some forms of attack from the internet - these are not new, they have always been there, it's just that no-one cares to try fix them any more :-(