Something that does not make sense

It is no secret that I think very highly of Les Miserables.  It truly is one of my favorite musicals. The songs are absolutely beautiful. There is a part in this story that I do not understand. My favorite character Jean Valjean makes no sense near the end of the second act. Let me explain.
    In the middle of the second act, Cosette and Marius get engaged. After Cosette leaves Valjean tells Marius his "confession". He also makes Marius promise that Cosette will never know the truth. Marius agrees to keep the secret. Then two songs later, when Valjean is dying, he Cosette a piece of paper. He says, "On this page, I write my last confession. Read it well, when I at last am sleeping its a story, of those who always loved you. Your mother gave her life for you and gave to my keeping." Then, he dies.
     This does not make much sense to me because at one point Valjean seems to be like 'Cosette should never know the truth'. Then, when he is dying he is like 'well, guess I need to tell Cosette the truth now'.
       I do not know why I think about that a lot. I guess it is something interesting to think about, I mean, I would not want my dad to lie to me about something until just before he died. I know that Valjean had his reasons, but, I think he could have done it a little better. I am not sure how he could have it better with exception that he does not tell Cosette the truth as he is dying.  When I first heard the musical, I thought he would never tell her. As he says in the song 'In My Life' : "You will learn, the truth is given by God to us all in our time, in our turn."  Guess he had a change of heart in the second act.
       Even though that did not make sense to me, I still love the character Jean Valjean. I can not wait to see Hugh Jackman play him in the movie coming out in December!!