Simplify the following text for a Grade 11 native English-speaking person.
Original: Because psychoactive substances bring about subjective changes in consciousness and mood that the user may find pleasant ( e.g. euphoria ) or advantageous ( e.g. increased alertness ) , many psychoactive substances are abused , that is , used excessively , despite the health risks or negative consequences .
Simplified: Psychoactive substances change the consciousness and mood of their user .