How to use "for good"

Do you know that there is another way to say "forever"?

Macmillan Dictionary - permanently, without the possibility of change in the future. It looks like Jamie has left for good this time.

Merriam Webster - "for good" also "for good and all":  forever, permanently

The Free Dictionary - forever; permanently. I finally left home for good. // Now she says she's leaving him for good.

But... is there any difference between "for good" and "forever"? 

I found a good explanation for this question here : 

'Forever' is much more dramatic - it means eternally, till the end of all time.

'For good' is usually used in the sense of everyday happenings in life. It would mean permanently, for the rest of my life.

This leads us to conclude that, when it comes to Portuguese, "for good" is the best translation for " definitivamente" : He left his job for good. (Ele largou o trabalho definitivamente.)

I hope it was helpful. 

Now, how about learning how to use it singing with Boyce Avenue "Back for Good"?
lyrics here 

Until the next time !! :)