Siebold begins with mental toughness secrets that we can all adopt. It is absolutely necessary that you, as a Catholic, use every means you can in your human powers to help yourself achieve holiness. God will give you his grace to make up for what you cannot achieve. Siebold's book gives 177 great hints for becoming much tougher, but the goal for Siebold is simply worldly success.
As Catholics, we do not strive for worldly success: we strive for heaven. Nevertheless, in our striving for heaven, sometimes we are given the gift of worldly success. It is tough to gain worldly success, but even tougher to gain sanctity. The motive behind us achieving worldly success must always be a strong faith, strong hope, and strong love for God and for others.
177 Mental Toughness Secrets of the World Class contains many resources for further reading, insightful quotes, and some very helpful tips and goals to push yourself to be better each day. Some of the quotes Siebold uses are shallow, and some resources he proposes seem too focussed on business success. Siebold avoids using reference to "God", but at times comes very close.
All in all, Siebold's book is very useful for developing mental toughness. It seems that his list is not exhaustive. The secrets he proposes are from a worldly perspective and are to be used in order to gain worldly success. Although Catholics do not see worldly success as evil, it can be evil if it serves to take us away from God.
I give it 7/10
God bless you
Pray for me