Perseverance (Preservation) of the saints is hardest for me.

When talking with others it is the system itself. Most very quickly see that Calvinism is a system--but systems have this stigma, whether rightly or wrongly, of being cold and austere. Men do not commit to systems. I can very quickly get people to see that Calvinism is utterly logical. But that is often the stumbling block. Cold logic turns into existential despair.

That is what I noticed in college.