our life/lives

It is possible to purify or enrich our lives by chanting the mantra. (plural)

It is possible to purify or enrich one's life by chanting the mantra. (singular)

It depends on what you are saying/want to say, T.

our life = the one we share as in John Lennon's song (Just like) Stating Over

Our life together is so precious together
We have grown, we have grown
Although our love is still special
Let's take a chance and fly away somewhere alone

If you mean lives separate and distinct and specific, then our lives

I'd say that it can also be used in a general referent manner, where,

It is possible to purify and enrich our life by chanting the mantra

can be glossed as,

It is possible for anyone to purify and enrich their life by chanting the mantra.