I used to have problems keeping up with post processing (PP) when I used Photoshop, but now that I predominantly use Lightroom I find PP much quicker and more enjoyable, as it does 90% of what I would typically be doing in photoshop with much less hassle and more automation, quicker and easier controls and menu access and lots of saved presets. Then if I need to do more I'll use photoshop for a specific picture. Automation and applying preset watermarks and so on are simple in Lightroom too.
That's been the biggest improvement I've made to keeping on top of PP, but it depends on what sort of pictures you're taking, whether you need a quick turnaround (if they were taken professionally for a client, for example) and what editing workflow you have!
Perhaps less helpfully, you could try not taking any miore pictures until you catch up
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Well, maybe not something as draconian as that, but just try to find time to catch up with your PP and set aside time to do it. Also, if the reason you are falling behind on PP is that you don't enjoy it as much as taking pictures, then you could try to set up everything in camera to minimise the time you need to spend afterwards doing fixes. But, again, it depends on what you're shotting whether that would be a reasonable measure.