Student or Learner
This rich man could have agencies on the lookout for men that had lost their grip on themselves; that had through indisposition weakened their will; that through some sorrow or misfortune had become discouraged.
I know what "get a grip on oneself" means, but never heard "lose a grip on oneself".
Does it mean something like "be out of one's depth"?
But if you were to paraphrase the phrase "lose a grip on oneself" how would you describe it?
To take leave of one's senses.
To be[come] a little out of control.
In each case, the metaphorical 'grip' is on one's presence of mind. Often the object is dropped: many WW2 films include the line 'Get a grip man' (where man is not an object but a vocative - not the case [Eng doesn't have it], but a form of address.)