The Sun represents the total potential of your being in this life, your life potential. Neptune rules dreams, visions and imagination; it is your capacity for illumination. The alignment of the Sun and Neptune reminds you that it is always possible to imagine what you wish to be, to dream or re-dream your life... and then make it so.
Neptune rules your perception of yourself and the world around you. You have a vision of what you are and what you face. But it is limited by your assumptions and consciousness of what is real for you. Your reality, your universe, is always circumscribed by what you perceive. You may share many of these perceptions with others and your reality overlaps with theirs.
The alignment of the Sun (Self) with Neptune (Illumination) allows you to perceive the truth that there are multiple realities in and around you. You actually live in one universe within a "multiverse". You have the opportunity now to let go of a lesser, more limited sense of yourself, at least for a moment or two, and discover a more complete you within a more integrated reality. Now you have an opportunity to dissolve, let go, dream great dreams, and move into a new space of self-realization.
This should be familiar to you; you do this all the time... when you are sleeping. Now, bring that wondrous experience into this waking world so that your dreams can become substantiated. It is confusing at first, but that is the path to a more complete understanding
Remember, the path of spiritual illumination leads from Certainty to the dawning of Doubt to a time of Confusion so that you may finally come to Disillusionment. It is then, when you have dropped your former assumptions and certainty, that Spirit will enter in and bring to you Illumination.
If you are certain then you are not paying attention; if you are questioning then you are preparing the way; and when you are Faith-Full then you are fully present and know that you can create whatever you imagine....and so you shall.