The termination of an activity, the pause when an impulse or judgement is finished — this is a sort of death, but no harm in it. Turn now to the stages of your life - childhood, say, adolescence, prime, old age. Here too each change a death: anything fearful there? Turn now to your life with your grandfather, then with your mother, then with your [adoptive] father. And as you find many other examples of dissolution, change, or termination, ask yourself: 'Was there anything to fear?' So too there is nothing to fear in the termination, the pause, and the change of your whole life.
In this passage, Marcus compares change to a type of death. Whenever you finish an act (end of a school period, end of a basketball game, end of a party), that act is now dead. Whenever you pause (mentally) before judging something, this too is a type of death. Yet you don't think anything of it. The end of these events is no big deal whatsoever. Moving on to grander events such as leaving childhood, entering middle school or high school or leaving home for the first time or buying your own home for the first time - these events too are deaths of a sort. In all this, you may experience a little anxiety, but there is nothing significant to fear. And if you pay close attention, you will notice that as you look back on these events, there was nothing to fear. In fact, you may even experience a sense of accomplishment and growing more mature. Your ultimate death will be similar - no need to fear. It is simply a change from one level of maturity to the next.
(see also Citadel p. 271)