The difference between "my life" and just "life" is that the former refers specifically to the life of the speaker. Without a determiner, "life" just refers to life in general or the lives of everybody.
Having a car makes my life easier.
This means that a car makes things easier for you.
Having a car makes life easier.
This is a more sweeping statement that suggests a car makes life easier for anybody who owns one.
Yes, you can use any possessive determiner such as her, his, their etc to refer to the lives of specific people, or groups of people.