Julie Skywalker wrote:^ In some cases other things are... especially around here.
And that's the difference between theory and practice.

Nah, but seriously. People always seem to think life works that way, but it actually doesn't, in my experience. For most intents and purposes, no one is actually obligated to do anything, especially in regard to little things like going kayaking. You have to weigh the potential costs and benefits of every action, and make a choice from there.
But, more often than not, what people don't realize is that it's okay to say no. So what if you don't go? Who cares. It doesn't actually matter.
Of course, the counterargument is that sometimes we have to do things we don't want to do, and that is indeed true. But sometimes is not always. Sometimes, we
don't have to do things we don't want to do.
More often than not, it goes something like this: "Blah, blah, blah, you have to do this, because I told you so."
Shuddup. No I don't. I'm not an enlistee. I am fully capable of making my own decisions, and I've decided I don't want to do it.
Depending on the context of the situation, any number of consequences could arise. But if the action in question really isn't important or worthy of your time, none of them will be negative.