Maybe you could look into exercise and nutrition. Spend some time researching it and then take action. Could be a fun, healthy, and positive way to pass time. I enjoy reading about stuff like that and sometimes spend several hours in a row just doing that. Just a suggestion.

You could look for a new hobby or try to improve certain skills (for example, increase your typing speed/accuracy). Volunteering is an option as well. Maybe you would enjoy some long walks during the week.