I am one of those people who suffers from an excess of duty: I fill my head with a lot of "should" and "ought-to", especially where Zen is concerned. Because Zen asks us to throw ourselves in to practice, to commit ourselves, it is easy to reach the point where we forget that practice actually can be enjoyable. You could read an awful lot of Zen literature, and listen to a lot of Dharma talks before you unearthed such a sentiment. There is such an emphasis placed on having a regular practice, that we can get to the point where we are slavishly going through the motions, as if conforming to some model of a Zen student will end our suffering. It won't. We need to be doing living zazen, and to appreciate that, maybe sometimes we need to take a break from it. Gasp! Having said all this, there's nought worse than a Zen slacker, "It's all Buddha mind, friend." Either you're practicing the Zen way, or you ain't. Reeling off the odd koan on a forum and "going with the flow" is also not going to help your life very much. I've used Zen as a way to beat myself up before now: I'm not doing enough zazen, I don't go to enough sesshins, I'm not sewing my rakusu quickly enough, and so on and so forth. It's not Cub scouts, you're not earning badges (funny, when I was a Cub Scout I got but one solitary badge....), you're not in a competition to see how "Zen" you can be. This excerpt is from "Not Always So", by Shunryu Suzuki, edited by Ed Brown:
"If we do not have some warm, big satisfaction in our practice, that is not true practice. Even though you sit, trying to have the right posture and counting your breath, it may still be lifeless zazen, because you are just following instructions. You are not kind enough with youself. You think that if you follow the instructions given by some teacher, then you will have good zazen, but the purpose of instruction is to encourage you to be kind with yourself. Do not count your breaths just to avoid your thinking mind but to take the best care of your breathing."
