How do I become optimistic?

Hi, I am at a point in my life as a university student i am constantly looking into my future and feel suffocated by these thoughts about how I will not get a job after graduating, I know this is probably not realistic as I am an overachiever but I still believe it and feel like my life is over :(

I would love advice from people who are carefree and optimistic, how do you do it?