The Sun is the source of all energies. These energies stimulate the activities of the houses occupied by the transiting Sun and reinforce or weaken the planetary effects, depending on the Sun's aspect to the natal planet. When the Sun transits an inner planet, it may trigger a dormant aspect between that inner planet and a slower moving outer planet. If a planet is being transited by another planet when it is being transited by the Sun, the effect of the transit is strengthened.
Sun Trine Neptune
Sun trine Neptune aspect will cause you to see each other in light of your relationship potentials and give you the kind of understanding which will allow each other to live up to the couple you could become. When the Sun person is trine the Neptune person your partner will inspire your natural creativity and love and harmony will flow through your relationship. It can improve mutual psychological insight into a relationship, especially in the realm of the subconscious and past conditioning.