Psychology teaches us that people will work harder to avoid a loss than they will to achieve a possible gain. A famous, successful investor admits that it angers him more to lose $100 than it excites him to gain $100.
You can utilize this with any kind of persuasion, whether it be sales, or helping friends make positive changes. Put them in a position where the perceived gain looks more attractive than the risk of doing nothing.
One non-sales-related hack to guide others to help themselves is to ask: “How would you feel if…?” This allows them to envision a world in which they have a successful career, a fulfilling relationship, or a substance-free life.