It's really a wonder that I haven't dropped all my ideals, because they seem so absurd and impossible to carry out. Yet I keep them, because in spite of everything, I still believe that people are really good at heart.

This quote is saying that it is a surprise that the person speaking has not given up on their ideals. These ideals may seem impossible to achieve, but the speaker still believes in them because they believe that people have good intentions at the core of their being. Despite any struggles or difficulties, the speaker still holds on to these ideals because of this underlying belief that people are ultimately good.