Diligence doesn't mean intensity.
It doesn't mean you have to sprint all the time. It doesn't mean working yourself to death.
Diligence is the constant application of your practice to the circumstances of your life.
Diligence is continued effort. Effort today, tomorrow and the next, month after month, year after year. Effort when times are good, effort when times are bad. Effort, when it is convenient and when it is not.
Your list of goals will change, your responsibilities will shift and flux, yet you continue with dedication in your practice.
That is diligence.