How to stay motivated in life when you don't have any support system? even your family?

It will require multiple approaches. The following is just one: Make a list of the things you need to do, do it on paper, not a computer. Do an easy one and mark it off, do the next one and mark it off. The act of marking off will create a sense of accomplishment and motivate you to do more. Wish you good health!

Definitely difficult specifically in the world we live in. Try getting involved in activities that bring you joy, spend time with people that care about you and can listen to you. Respect your body, eat and rest well.