To resolve to do something is to decide firmly on a course of action. For a leader, it means closing off of some alternatives and visions so that you can direct all of your resources and time into one coordinated effort.
When you resolve to do something, you do not waffle, waver, or wander; you step out confidently in a predetermined direction. Strategies for reaching your vision can change. The timeline may be modified. The team may be shuffled. But, ultimately, your vision and conviction must stay the same. Your initial resolve is the foundation on which the entire structure of your efforts will be built.
Beware that your resolve is weak when you struggle to answer these two questions:
Why am I doing this?
Can I achieve what I have set out to do?