Not everyone is relaxed on the weekends some people even have to work on the weekend.
When I was younger I worked as a grocery clerk and the weekends where probably the busiest/most stressful.
What can make you relaxed on the weekend is if you get that time off from work. Work can be a lot of stress for someone and not having the stress can make you feel relaxed.
Also free time is always relaxing! At least usually, since you are doing what you want and on the weekend you have more free time then you do on the weekdays (if your work schedule is like that) which would make you feel more relaxed.