Life Sustainment actions are those that tend to preserve some pleasant state or condition in your life. For example, brushing your teeth preserves a state of good oral health and allows you to keep your teeth throughout your life. Work is essentially a sustainment action, since it provides income that, in turn, is required to complete other actions, both sustainment and improvement. A common characteristic of sustainment actions is that must be done over and over (that is, they recur), often at a regular frequency. And this recurrence happens at different levels of time scale: some must be done done daily, some weekly, some monthly, and so on.
All Life Sustainment actions are directed at reducing loss, either by preventing it, recovering from it, or both. These can be considered Loss Prevention and Loss Recovery.