Use it or lose it
It means that if you don't continue to practice or use an ability, you might lose that ability.
Additional Information
Examples: If a person doesn't exercise his or her physical body, he or she will likely lose strength, stamina and endurance. The same applies to a person that doesn't practice a new skill, whether it is learning to drive, speaking a foreign language, etc. he or she may forget or lose those skills.
Phrasal Verb：
To zero in on
Definition: to focus closely on
Example: “We can zero in on the candidates for this position during the interviews. Right now we can only see how talented they are on paper.”
