What is the term for two mutually exclusive, contrasting emotions I am a psychology student and I vaguely recall a term being used to describe two emotions that cannot be expressed simultaneously. The example was fear and relaxation in terms of Systematic Desensitization. Can anyone help me out with this? Many thanks in advance.
In terms of systematic desensitization, you're thinking of reciprocal inhibition (see, e.g., Wolpe, 1954).

For what it's worth, beyond this literature, there's a general debate about whether positive and negative affect can be experienced simultaneously.  (Indeed, Emotion Review just published a series of articles about this.)  It's fair to say that the debate has not been resolved.