Humans have an excellent brain that helps them to imagine and hence plan for future ahead. But qualities similar to these are anticipation, anxiety, expectation and frustration. In all, it is all in our minds. The emotions too.  When our "logical" brain tells our body not to shake legs or bite nails when nervous, not to cry when betrayed, not to shout when overwhelmed, not to laugh loud when feeling exhilarated, then we are actually wiring our brains to suppress our feelings and natural responses. Sometimes this suppression carries on for long and the hormones related to that particular emotion...