You would not use our if life is singular, because we do not all share the same life. You would only use our if you are using lives. It should be: Most of these stressors are commonly found in daily life. This means: Many of these sources of stress are normally encountered on a daily basis. It could be: Most of these stressors are commonly found in our daily lives. This means: We often encounter many of these sources of stress on a daily basis.

In both sentences "Most of these stressors are commonly found in our daily life." "It is common in our life/lives." It is necessary to use "lives" because of the use of "our", since "our" is plural. If you want these to be in the singular and use "life" then the "our" must also be changed to singular and by "my" or "your".

"Most of these stressors are commonly found in daily life." "Most of these stressors are commonly found in daily lives."