תרגום - פינית-אנגלית - Tämän tunteen tuntee vain kerran elämässään.

Sometimes we translate things of this sort with "we": We know this feeling just once in our lifetime.

Would that work here?

Yes. It would keep the meaning.

Good - I've changed it now.

I think "we" isn't the best possible translation here since the original writer is trying to express her love and may be quite unshure how the other feels.

I would translate this "This is something one feels just once in lifetime" or something like that.

I would interpret this as the impersonal "we", meaning all of us.