Lately I've seen a lot of TV ads for eharmony. They claim to be able to put you in a good relationship based on mutual compatibility. Never mind that, many times, we are more charmed by the people with whom we're not compatible, or who are bad for us.
Or, for better or worse, often our compatibilities are pathological. My need to help matches your fear of taking care of yourself. Your unwillingness to take responsibility for your life matches my demand for control, etc. Sometimes we call this kind of thing "ministry," but then again, it's often easy to use religion to gloss over unhealthy dynamics.
Nevertheless, compatibility is critical. St. Irenaeus, whose memory we celebrate today, knew all about it. His Against Heresies is a brilliant text, and worth reading. He begins a theological reflection on the "economies" of God. This is to say that he tries to give an account of God through how God works on our behalf. Thus he comes to an account of the Incarnation:
The Word of God which dwelt in man was made Son of man to accustom man to perceive God and to accustom God to dwell in man, according to the good pleasure of the Father. (Adversus Haereses II:19:3)
A short statement but a deep one. God the Father is a love so generous and self-diffusing that he wishes to share even the divine life with us. His Word becomes one of us in order to establish a permanent affinity or compatibility between human and divine. The infinite distance between God's greatness and our littleness is overcome in Jesus Christ. Human and divine become compatible.