A man who gives way to hate and broods over his wrongs, will be

led to think of murder, and if he gloats upon thoughts of murder a time

will come when he may attempt murder. On the other hand, if the same

man will keep his mind off his wrongs and think thoughts of forgiveness,

or, better still, if he will love, or hold in thoughts of good-will the one who

has wronged him, then his life will become happy and peaceful, and in

its highest sense, successful.

Does it mean "if he will think kindly of the one who has wronged him ..."?

Yes, that's the idea.

Thanks Clive!