I'm sorry you're bummed.

Just keep at it. You'll get your mojo back. What is making you feel like going slowly right now? Fitness? Fear of obstacles? General unsteadiness? Lack of confidence?

I'm mostly a mtb newb myself, but it helps if I'm focusing far enough down the trail to anticipate what I need to do and if I'm using the various body positions at my disposal. I'm quick to get out of the saddle in ready/attack mode if I'm at all uneasy/unsure about what to expect. And I try to remember that momentum is generally my friend. Not only does it make getting over obstacles easier, the bike is easier to handle, too.

The renewed confidence will come with time. Stick to trails that you're familiar with. A few good passes will do wonders for you. Perhaps some skill drills will help you, too. Go back to the basics.