Sail(ing) dream meaning is explained below using 3 different sources. Each interpretation is shown with its source.

Interpretation 1 — Stearn Robinson - Tom Corbett

If you dreamed of handling or observing the sails on a boat it predicts approaching happiness; to dream that you were sailing under pleasant conditions and with favorable winds predicts prosperity, but uncomfortably choppy seas or dead calm portends disappointment If you dreamed of sailing into harbor in a small boat the forecast is of sudden success or unexpected good fortune.
Source: The Complete Guide to Interpreting Your Dreams Author: Stearn Robinson - Tom Corbett

Interpretation 2 — Dream Explanations - Anonymous

To dream of sailing signifies that you are in rhythm with the ebb and flow of life. Sailing also denotes that you are enjoying a relaxing life and that you are feeling free to express your creativity. Because sailing is a water sport, this dream symbolizes your connection to your emotions, your unconscious, and your deeper feelings, longings and desires.
Source: Strangest Dream Explanations Author: Dream Explanations - Anonymous

Interpretation 3 — Margaret Hamilton

See “boat”
Source: Dream Dictionary Unlimited Author: Margaret Hamilton