Working on a computer can actually be a relaxing activity. Correct posture for this activity can give you the energy to make it through the day.
Some of the recommendations for good posture offered by physical therapist Lorena Jiménez Franco are to ensure the proper placement of your feet and hands, keep your back straight, and place your computer at eye level. See also Safe posture when standing
The following video provides suggestions that can be used on a daily basis, especially if your job involves working in front of a computer. Also, remember to take active breaks in the morning and evening. See also How to improve your posture when you walk