Longing for something causes no harm, but the inability to turn that desire into action harms many. When you come up with something you most definitely want to pursue, you may be at a loss at first, it may seem impossible. However, seek to understand what you need to achieve this goal. Do you need a mentor? Do you need to gain a new set of skills? Do you need to first learn about a new industry? If you think "someone else would have done it" or could do it better, you need to stop and realize that "someone else" is too busy minding their own business, and it is your turn to be that person that makes a difference in some area. So find that drive and get moving.
Problems are only daunting when you don't know what's the next actionable item that will get you closer to your goal. As such, always think, what is the very next step I need to take to get one step closer to my goal? Once you have that figured out, just go ahead and take that one step.
"A journey of a thousand miles begins with a single step."
- Lao Tzu
Once the journey is over, you'll look back and be glad you took that first single step, then the second, and the third. But if you never take the first step, you'll always wonder "what could have been if?"