What does it mean when Cicero expresses the tendency in human nature by saying "construe things after their fashion, clean from the purpose of the things themselves." How does it relate to the action in Act1 Scene3?

We ourselves can create ideas, theories, and even assumptions about why things happen the way they do, according to our own belief systems, which are in most cases biased. Unfortunately, this also means that we don't see the whole picture, and what we actually see may not be true for any but ourselves.

Why does Shakespeare make Caesar change his mind so often in this scene? (Act II-Scene II)