Naps are awesome. It really is as simple as that. Sleep is always at a premium when raising kids, so there are going to be those nights where you just don't get quite as much as you need to keep functioning at a high level. Could you push through and make it? Of course you could, but man, it is so much sweeter to just give in to that wonderful mid-day slumber.
My kid wakes up between 4:30-5:00 AM, so getting enough sleep can sometimes be an issue when I stay up a little later than planned. I know my body fairly well, and at 8 hours, I can take on the world, at 7 hours, I feel pretty great, at 6 hours, I can manage, but once I get down to that 5 hour range, I'm going to be struggling. I can manage it when necessary, but the brain is only performing the most essential functions by the time I get to the mid-afternoon.
Luckily, my kid takes two naps during the day. The morning one isn't that prime for napping as I still have enough energy, even on a poor night of sleep to keep my energy up. But that afternoon nap, man, that is some primo napping time. He gets 1.5-2 hours of sleep, usually around 1:30-2:00, it is prime real estate to get that battery recharged. He's sleeping; I'm sleeping. It's wonderful.
But don't let the pursuit of ideal circumstances prohibit you from your napping destiny. I'm in a privileged situation when it comes to napping with a partner to help me out as well as just one child, so I can tag out on some tired afternoon and have the Mrs. take over so I can get some rest, and she can always do the same when necessary. But if you have any help available, find a way to utilize that to get a nap on those days when you're mind is crawling along. Have somebody come over to your home and have them take lead so you can retire to the bedroom and get a little shuteye.
The beauty of naps is that they don't always have to be long. Sometimes, I wake up from 15-20 minutes, and although I'm not fully refreshed, I have at least gotten charged up enough to get myself through. But when you get that good hour-plus, you're back to running on all cylinders. Sure, you may have missed a little time here and there with your kid, but the time that you are there is more valuable, because you're able to be more engaged in everything that is going on.
If anything, you should feel guilty for not taking a nap.