When it is obvious that the goals cannot be reached.... All goals will have a way for you to reach them. Sometimes the actions you need to take will have to be altered or even changed.
Don't adjust the goals, adjust the action steps.... It's always much easier to adjust the action steps to reach your goals than it is to live with regret because you gave up on your goals or you adjusted your goals because you ran into a road block. Never give up on the goals but don't be afraid to adjust your goals.
GO FOR IT, YOU CAN DO IT!!