It's well known that stress weakens the immune system[1]. So it's not a surprise that stress might encourage dormant infections (such as HSV-1) to enjoy a resurgence.
Speaking anecdotally, sleep deprivation is the biggest immune system damper for me. Often it’s hard for me to judge the effects of stress per se, because sleep deprivation also leads to stress and vice versa.
[1] https://www.apa.org/research/action/immune