Sadness is the state of being unhappy or being upset about something. It can be set on by a variety of different things.
Positive: Dreaming of being sad can represent a heart of repentance unto the Lord, but it is important to not let it turn into condemnation. Godly sorrow leads to repentance and salvation.
Negative: In a dream, being sad could represent a spirit of heaviness or spiritual death. It could represent a need to praise often in one’s life. Dreaming of sadness could represent pride through self-pity.
(2 Corinthians 7:10).