Some background information: "Just a matter of (something)" is an expression to describe something that is obviously needed or expected for something to take place.
It's just a matter of time before they catch the fugitive (little time is needed).
It's just a matter of drill and practice for him to ace the test (drill and practice is obviously what he needs).
This (something) can be a noun (i.e practice) or a gerund (i.e. practicing). I tend to hear "just a matter of practice" though.
I hope this helps.