Technically not true, as of course we always "know" more than what we did yesterday, it's just that knowledge we gain often puts into perspective how much more we don't know. As I was pursuing my undergrad I had a strong mix of Theology and Psychology thrown at me. The Biblical studies really helped me define and expand on what I believed and created some of the most edifying relationships with professors that loved God. The Psychology really helped me to better understand the human mind, not only just how it works and develops, but also how individually different they are for each person that is the result of God's work and their unique experience.
What is most interesting about Psychology, that while it is a science, it has many limitations in application and scope that other scientific fields don't typically encounter. For example: mathematics in China can be used in the same way to solve the same problems in England. Logic flows that a cure a doctor might use for yellow fever will work in Africa the same way it might work in South America. Psychology is all about the mental faculty of humans and this mental faculty is made up of our own individual experiences, relationships, biology, and culture. This science has to adapt to each of these factors, and that introduces no small amount of challenge.
The deeper I went into Psychology and Japanese culture, the more I realized how "western" this science is. I think many people already know that a healthy secular mindset as presented by a therapist will be very centralized with the patient focusing on themselves and doing what is best for them: that they should be all about themselves and they alone have the power to realize this (this is oversimplified, but we've all already heard this one) In Japan, this idea is completely wild and unacceptable. The Japanese are very much about what is best for the group as a whole, and not that of the individual. In fact, the people of that nation have a phrase that is commonly used, "This is very Japanese of me to say but..." which one might translate as, "I know what I'm about to say doesn't make sense, and might even be considered wrong, but it is what I believe because it's the most appropriate response".
So it took me 4 years of college and now almost 2 years of graduate school to realize I'm not getting what I need? Not quite: I certainly gained some useful skills, and it sets me up to pursue that PhD as originally intended, but instead of pursuing that in the US, I'm going to wait and do most of it in Japan. I realize this means a very high level of language fluency, but that was always part of the plan. What I really need is that deeper level of cultural understanding of the Japanese people and I'm not going to get that over here no matter how many classes I take. Of course this will also have the benefit of knowing more effective ways to minister and disciple, but that is an entirely new topic on its own.
So even as I wrap up this Master's I know I have quite a few more years of study ahead of me, and I'm very thankful for that. God has given me such a passionate yearning for the Japanese people and culture, and the thought of pursuing education in that very context to help give me the tools for ministry towards sharing Jesus and combating suicide is nothing short of a blessing.