First, Diego examines the opinions he has formed about Erika. He likes that she is friendly and mellow, but is less than thrilled that at times she can be boring and self-centered. He is physically attracted to her and he thinks their chemistry is amazing. He knows he is not yet in love with her. Diego synthesizes this information in what he feels is a logical way: since he likes four of the six aspects he identified (her friendliness, how mellow she is, her looks and great chemistry), he proceeds to pursue a relationship with Erika.
Although the decision to be with Erika may end up being right or wrong for him, Diego's process in making that decision was faulty. What he should have done was separate each of the factors he thought about into the Relationship Essential categories. What this does is make sure that Diego is thinking about Personality Fit, Magnetism and Love separately.