Creek and ditch crossings require a little bit of forethought. Sit back in the saddle and lift the front wheel- and pedal like mad. A light front wheel will not stick in the soft mud and the pedal like mad is to get the rear wheel through.

And I am sorry- A mountain bike is not a mountain bike untill it has a few scratches on it. I was always worried about a new MTB until I had taken it to its limits- or mine- and then scraped it along the trail. Teaches you to fall properly and if you do that often enough- you become expert at it.