To dream that darkness comes upon you indicates defeat in a project that you might try. Darkness is symbolic of incomprehension, the unconscious, malice, death, and concerns about the unknown. If the sun pierces the darkness, you will be able to defeat the obstacles in your way. If you feel confident in the darkness, then you don't need to understand everything about things around you. The phrase 'ignorance is bliss' fits here.
To dream that you can't find someone in the dark suggests that your anger needs to be reined in and controlled. You allow your feelings to get the best of you.
To dream that you are lost in the darkness indicates a sense of despair, sadness, or uncertainty.
To dream that you are groping in the darkness signifies that you do not have enough knowledge about a particular topic to form a valid decision. Dig into the topic and don't make snap decisions.