Missing one Zoloft/Sertraline shouldn't cause this, should it?

I woke up perfectly fine today, looking forward to the day. I got really tired at one point so I decided to take a short nap. When I woke up, I was really down, and I then realized that I was about 6.5 hours late in taking my anxiety meds.

As far as I know, though, the meds are designed to stay in your system for quite a while, right? So I can’t imagine this happening when I didn’t even miss a full day. On the other hand, there’s nothing I can think of that should have made me feel this crappy.

Not really looking to hash out my feelings, I’d just like to know if missing one pill at my regular time is even capable of doing this. Thanks.