Within an ace of something/of doing something
Definition 1 of 1
Pro Tip 1/3Near Success
This phrase implies being very close to succeeding, often followed by a sense of tension or excitement. 
She was within an ace of solving the complex equation.
Pro Tip 2/3Almost Failure
It can express a narrow escape from failure or disaster, underlining relief or luck involved. 
The explorer was within an ace of falling off the cliff.
Pro Tip 3/3Emotional Intensity
Use it to highlight the emotional intensity of being very close to a particular outcome. 
I was within an ace of tears when I heard the news.