Schedule a Time to Play
One of the best things you can do if you are busy is to schedule time to play. Yes, put down an hour or two in your calendar to play Black Ops 3.
This is a tried and true trick to working out more and to carving out time for other activities. If need be, share the calendar with your spouse or significant other.
Another trick is to find other players who can join you. Obviously the first choice is your friends, but schedules and console ownership may not line up when time is limited.
If that is the case use services like Reddit to find other players who want to play the game types you like and can play at the same time.