St Thomas and modern psychologists consider emotions differently. In fact, St Thomas has many different terms (affectus, caro, passio, etc) for what in English we simply call ‘emotion’. But St Thomas never uses the term ‘psychology’; in fact, this is quite a new field of study which doesn’t really emerge until the 19th century, largely as a result of Enlightenment dualism.
St Thomas’ treatment of the passions and affections is quite complex and very different from modern treatments of emotion as ‘feelings’. Briefly, St Thomas’ study of the passions and affections is intimately linked to his study of the whole person, and the nature of person as either virtuous or vicious. For St Thomas, the human person by nature is oriented towards the good and so love is the first passion which orients us in this direction. He considers passions, in general, in their capacity to either help or hinder the human person, through reason, determine the good and ultimately seek God. Modern psychology has no interest in the human person as being oriented by nature to the good and ultimately to God; when it does consider goodness or God, it is from a purely subjective point of view, as though these things are merely projections of the individual independently of any supernatural orientation.
I highly recommend an excellent and quite recent study of emotion and affection in St Thomas by Nicholas Lombardo, OP.
amazon.com/The-Logic-Desire-Aquinas-Emotion/dp/0813217970