Point of No Return?

In the life of a born-again believer, at what point does his sin negate (or outweigh) the good works he has done?
Recently, a friend and colleague from years ago was found dead in his home by his wife. The church where he pastored and the school where he taught joined together to honor his life in a memorial service at the school.
Now, one week later, the man's son revealed in another gathering at the school that his father had admitted to some bad decisions in his life, and committed suicide. A note was left, detailing his depression and his sin (including membership on AshleyMadison.com), and saying he was very, very sorry.
His wife said she and their children would have forgiven him and moved ahead, as would many others in the school and church. Speaking to news sources, she said, "What we know about him is that he poured his life into other people, and he offered grace and mercy and forgiveness to everyone else, but somehow he couldn't extend that to himself."
I remember nothing negative about John. Not one thing.
God knows my own sins are terrible. They are sins, after all.
Am I no longer fit to serve in ministry because of my divorce? Am I no longer called by God to teach and/or preach?
Among my friends are those who say that I am still qualified and called, as well as those who say that I am not. I do not doubt both groups love me, nonetheless.
Does my divorce outweigh any good I have done? Again, two camps, and within each, many degrees.
What about John? If he had not taken his own life, what would or could have been the outcome?
At what point do you - you, personally - reach the line where there's no going back, and the one or three tragic decisions outweigh every thing else?
At the point of genuine repentance? That takes time to ascertain, doesn't it?
Please, what are your thoughts? I'd really like to hear from you on this.