I agree with Jon. If what you're doing works then that's great. But to be able to 'do the right' strumming pattern will really help your coordination skills, especially starting out. It's a way of stretching your brain and muscle memory too. I see practicing as a way to stretch your boundaries, whereas playing is about having fun and just going with the moment. But in the end, as long as the pulse of the rhythm and feel of the rhythm is there, that's all that really matters.

Hope this helps as well!
Craig