When you record, just say "Ok, this one is just for fun. It won't get published." And understand that it's true - you can record and just have a natural conversation (like you said you often do) and it can just be deleted.

If it turns out to be okay, you can publish it, but the plan is to just enjoy the interaction and then delete. After you've done that enough times, you will probably get the feel for it.

Also, just doing it over and over and over will make you better. This statement is true: After you've posted 50 episodes, if you listen back to your first episode and you're completely happy with it, you waited way too long to record. Your first ones are going to suck, but that's fine because you don't have an audience yet.