If a person feels that his or her life isn't that stable, what is the best way to change that?

Get help. Depends on what you mean? Financial, relational, others. Seek a counsellor of some type or many types. Get a mentor. Seek help from someone your know and respect and see if they can give you advise and mentoring on life issues. See a credit counsellor, see a marriage counsellor, see a life coach, see your clergy, see the employee assistance program at work. Just act and do something!