I can't seem to focus on exercise and nutrition at the same time — it's always one or the other. How can I get both going at the same time?

Perhaps your focus is temporary. You mention focusing on eating clean and exercising as being daunting. How difficult is it for you to maintain your focus on brushing your teeth everyday or taking a shower? It's probably fairly simple. As a child you may not have wanted to do those "chores" but then you mastered them as a habit, made the connection between health and hygeine, and now it comes easily.

If you are focused on your eating as a diet, then you are right - once you take your focus away, you'll fall into your old eating patterns. However, what if you decided that, like brushing your teeth or taking a shower or even breathing, that healthy eating was a part of your life? And instead of worrying about taking it all on at once, you focused on transforming your eating habits so instead of going on a diet you could be happy because "this is the new way that I eat." And it doesn't have to be chicken and broccoli .. have fun, spice it up, enjoy it - this is what you will be eating not for several weeks until you reach some magic goal weight, but for the rest of your life because your body deserves to be healthy.

If you take that approach, then once you master the healthy eating, it shoudl be as easy as brushing your teeth or taking a shower, and then you can focus on making exercise a habit, too.
And don't fall into extremes. You want pizza? Enjoy it. Just not every day. Have it once in awhile, savor it, don't stuff yourself, and embrace healthy living.