They say revenge is best served cold. There is perhaps no other feeling that can top the feeling of getting revenge on someone who wronged you. Much like relationship troubles, being wronged by the enemy can consume your thoughts and leave you feeling terrible, though the need for revenge can also consume you.
In most cases, it’s never worth it to get revenge if there are bad consequences for it. It is much healthier to just let go of the hate, and not renew the cycle. However, most of the population have weak willpower and cannot even control their own diet, let alone more serious mental feats.