I've found that no matter how well someone plans, no matter how consciously aware they are of their activities, there are always points in someone's life where the upcoming tasks can seem a little overwhelming.  I have a couple thoughts on that.

1.  Breathe.  Oxygen is good.  Try taking 1/2 an hour to step aside from the daunting tasks at hand and just breathe; deeply and fully.  Think about what it is you really have to do.  Jot down the tasks (all of them) and visualize the people, experiences and other resources you could pull from to help you up the mountain.   In my experience I've learned two valuable facts that are applicable in most any situation. 

        One, people want to play a role in your greatness.  The larger a task you have to overcome, the more people want to be involved and contribute in someway.  Let them know how much you appreciate their contribution, and you'll be amazed how much they will accomplish for your dream. 

        Two, nothing is as big as it seems.   Our subconscious can play tricks on us though, which is why it's important to spend a little time considering the task before jumping into it head first. 

2. Understand how you got here.  As is typical of high performance people, you most likely have a tendency to take on tasks that stretch you; roles and responsibilities that challenge your limits.  This is a good thing.  Just remind yourself that this is a choice you made, and regardless of the outcome, you will be better for it, as it will have developed you more as a person than you could have possibly experienced had you chose the easy way out.