Sun Conjunct Moon in Depth
Why zero degrees behaves the way it does
A conjunction is not really an angle at all. It is the absence of one. Sun and Moon occupy the same slice of zodiac, so there is no vantage point from which one can observe the other. Everything they do, they do together, which is why this placement reads as unified rather than harmonious. Harmony implies two parties agreeing. Here there is only one party.
Most astrologers allow eight to ten degrees for a Sun-Moon conjunction, wider than for any other pair, because these are the two visually largest bodies in the sky. The tighter the orb, the closer your birth was to the exact New Moon, and the more the fusion dominates the chart. At six or seven degrees you get flavor. At under two degrees you get a defining feature.
The blind spot, and how it softens
Because your will and your feelings never disagree, you rarely have the internal argument that teaches other people self-observation. You want something, you feel good about wanting it, and you move. In your twenties this often reads as refreshing certainty. It can also mean you genuinely cannot tell when you are being unreasonable, since there is no dissenting inner voice to flag it.
The maturing version of this aspect usually arrives through other people. Partners, close friends, and colleagues end up serving as the external Moon that your chart did not supply internally. People with this placement who grow well are the ones who learn to actively solicit reflection instead of waiting for it. Asking a trusted person how you came across in a meeting is not weakness here. It is a workaround for missing hardware.
Natal signature versus the monthly transit
Natally this is a lifelong condition. As a transit it is your monthly New Moon phase, when the transiting Moon crosses your natal Sun for a few hours, and once a year the transiting Sun crosses your natal Moon for about two days. The annual Sun-to-natal-Moon pass is worth tracking. Many people find their emotional weather becomes unusually legible during those two days, as though something normally private is briefly lit.
If you were born under this conjunction, your solar return and your lunar return fall close together every year, which tends to concentrate a lot of personal reset energy into one stretch of the calendar rather than spreading it out.
Practical use
Put your birthday season to work. Because your natal New Moon repeats as an annual solar return conjunction, the weeks around your birthday are unusually good for starting things you intend to carry alone. Conversely, avoid making decisions that require a devil's advocate during that window, since your certainty peaks exactly when your self-doubt is lowest. Schedule one honest conversation with someone who will push back before you commit.