It is okay if you don't want to go to the barn today. It is okay if you don't want to go to the barn this week. It is okay if you don't want to go to the barn this year.
In this age of social media perfection, sometimes we feel overwhelming pressure to show up every single day. To wear perfect #rootd, take selfies in the polished dressage mirrors, and keep our horses immaculate.
To be quite honest, your horse won't be offended if you don't show up, assuming he has properly stimulating care (i.e. plenty of time outside and access to other horses). Will he get out of shape? Absolutely. But I can guarantee you you will have a worse impact on him than losing some muscle mass if you show up and don't want to be there.
I've seen a lot recently on the prevalence of burnout in today's society, especially with the advent of social media, and I think it has sunk its fangs into the equestrian world too. Would it be amazing if we could all get everything we need to do done and ride our horses every day and be incredibly happy while doing all of it? Sure. Is that real life? No. As someone who has been in the depths of burnout, and tried to continue going to the barn, I have news for you - It. Is. Not. Worth. It. You will get frustrated over silly things. You will lash out at your horse, or at yourself, or both. You won't pay enough attention to the details and your own safety, because you're simply there to check a box. Showed up to the barn and got a Good Horse Mom award, check.
Take some time over the next couple of days to evaluate your riding habits. What are small parts of your horsemanship you can improve without overwhelming yourself? If you don't feel like riding, maybe try some in-hand work (this has been a lifesaver for me when even lifting a saddle seems like too much). If you don't feel like in-hand work, maybe just give your horse a brush and some cookies. If you don't feel like going to the barn, maybe read some articles or review some tapes of your riding. You can do it, but you don't need to beat yourself up when you can't. Your horse will still be there. You have to be here too.