do you have a deadline to meet?
if yes: do you have shit to do?
if no: great. keep it up.
if you don't have a deadline to meet, and if you do have shit to do, then a plan may not be necessary. working out 4 times a week until exhaustion you'll see steady improvement, and be able to go about your daily business without suffering. the hard part about being in good shape cardio-wise isn't getting there imo, it's staying there.
think of a long-term goal, and what your schedule will allow for you to maintain that goal.