Specifically, loneliness, environment fatigue, issues with boundaries, and social disconnects with coworkers can all make remote work emotionally difficult.
Try to stay on a regular schedule and keep your work to a specific location. This reinforces the mental separation between what is work and what is home-time.
Your coworkers may not be close friends, but interacting with others regularly is important for mental health. Those who WFH may need to supplement that need.
Sitting still at a desk or on a couch all day is not good for the mind, body, or spirit. Take breaks to stretch, move around, and maybe get outside from time to time.