It depends on what you mean by cursing. A mortal sin, as you know, has three elements: Sufficient gravity, full knowledge of the gravity, and full consent to do the sinful thought, word, or deed anyways.
Someone like me (who used to be a habitual cusser, using cuss words as adjectives and adverbs liberally) is probably so unconscious of the fact that it diminishes culpability to a degree. Nevertheless, I confessed it, was told it was a venial sin, and that I would have to keep praying for the grace to avoid it, as well as the grace to better manage the emotions that provoked it in the first place. I was told to meditate on my relationship with God and how God sees me through His eyes and take that into account when I felt my temper rising.
My experience with doing my penance for this (including frequent reception of the sacrament of reconciliation and the Eucharist) and becoming more aware of the propensity to cuss helped me reduce the degree and frequency very significantly. I’m aware of the rising frustration, can use a brief mental prayer to decompress a little, and can state my thoughts much better and more appropriately. I don’t think I’ve used the “f” bomb as a conversational modifier for a couple of months now, for example, and don’t even use it when provoked.
My whole attitude for confession is this, and I was told it’s a useful attitude by my regular confessor: If something I’m doing is bothering me, it’s probably a valid topic to bring up during the course of a session in the confessional, even if it isn’t necessarily a mortal sin. Of course, when I’m struggling with something, I don’t just line up for the “box” during regular confession times, I make an appointment and go in to discuss it.
Hope this is of some help to you.