It is very important that people on dialysis do some form of exercise. It helps keep the body and mind active. Start small. If you generally feel very weak and tired and are lying on the bed almost the whole day, take a small step. Maybe, just sit up for a while. Slowly increase this. Then take a few steps around your room. Then walk around your house.
For people who are mobile but don't do any exercise, start by walking slowly for maybe 5 minutes every day. Slowly increase this to 10 minutes and then gradually to half an hour.
Any form of exercise will help. Walking is generally the safest. There are many people on dialysis who do more strenuous things like swimming and trekking. So, it is not impossible to exercise. Of course, check with your doctor before doing anything different from what you are used to.
Exercise will make you feel more energetic and active. It will make you more cheerful.
Try to do something you enjoy. For example, playing a game you like may be more fun and motivating than simply walking. But remember - don't take on too much at once. Take small steps. Gradually increase the level of exercise.
You will feel much better and won't want to give it up!