I tend to use the human potential framework. As a human being, I have a potential capacity to do sophisticated things or to merely operate at the level of an animal. Developing capabilities & skills is what differentiates me from an animal. This always fires me up.

Second thing that helps is, defining "huge" within the right context. Your project looks large from a self-centered point of view. Think about human flight - took 2000 years, multiple generations to figure out. Go into the history of various inventions, they all took lots and lots effort. Once this context is understood, you'll find that whatever you're doing is not necessarily such a "huge" task. Such perspective helps too.

Third, the characteristic of good goals is this:

Good goal = Difficult + Specific

The whole point of good goal is it helps you extract more effort from yourself. In a way, you set goals so that you can do more. If your goal demands more of you, it means the goal is doing its magic! So why'd you become discouraged when a goal demands more of yourself? By stretching yourself, you'll become more capable.