Since you mentioned character and self-help I am assuming you mean success and making this life a good one. For this I can suggest the following:
“The Catholic Book of Character and Success” by Fr. Edward Garesche (Sophia Institute Press, 2003). This is an edited version of Fr. Garesche’s “The Will to Succeed” (P.J. Kenedy and Sons, 1931).
“How to Get On” by Fr. Bernard Feeney (Benziger Brothers, 1891). Available free in pdf and other formats from the Internet Archive (a great source of old Catholic works in the public domain).
archive.org/details/howtogeton00feenuoft
I agree with Bravo 6 about anything by Venerable Fulton Sheen is the best there is. He is very good on all topics, including psychological health and happiness and successful living. Regarding good living, success, happiness I would suggest: “Way to Happiness”, “Way to Inner Peace”, “Walk with God”, and “Life is Worth Living”. In “Walk with God” you will find the essays: “Singleness of Purpose”, “Making Up One’s Mind”, “Manners”, “Habit, Not Instinct”. In “Way to Happiness” you will find the essays: “Self-discipline”, “Kindness”, “Work”, “The Idle in the Workplace”, and many others. In “Way to Inner Peace” you will find the essays: “Right Attitude Toward Those Who Differ From Us”, “Patience”, “Silence”, and many others.
Some others I might recommend are biographies of Vince Lombardi. Lombardi was a life-long daily communicant. He had a rosary on his car’s steering wheel. His approach to life and success was formed by his Jesuit education at Fordham in the 1930’s, and especially the teaching of his Jesuit ethics professor, Fr. Ignatius Cox, S.J. Two good biographies are “Vince” by Michael O’Brien (William Morrow, 1987) and “When Pride Still Mattered” by David Maraniss (Simon & Schuster, 1999). Lombardi believed success in life and in everything comes from discipline and hard work. He had in his study a framed and illuminated quote from St. Paul’s Letter to the Corinthians: “Brethren: Don’t you know that while all the runners in the stadium take part in the race, only one wins the prize. Run to win.” From the Jesuits at Fordham Lombardi learned well that we as Christians are required to constantly strive for perfection inspite of the fact we will never attain it in this life. On his first day at Green Bay Lombardi told his players, “We are going to relentlessly chase perfection knowing full well we will not catch it, because nothing is perfect. But we are going to relentlessly chase it because in the process we will catch excellence. I am not remotely interested in beng just good.”
The last recommendation reminds me of a few more works. “The Groundwork of Christian Perfection” by Father Patrick Ryan (Benziger, 1910) and “The Narrow Way” by Father Peter Geiermann, C.SS.R. (Benziger, 1914). These two works are on the Internet Archive and can be downloaded as pdf’s at:
archive.org/details/groundworkofchri00ryan
archive.org/details/narrowwaybriefcl00geie