What is your current condition? Like are you a NEET, or do you live a mostly normal life?
I've had SAD a looongg time. When I was in K-12, it was awful. Wouldn't talk at all in school, burst into tears when I was put on the spot during class, couldn't ride the bus, had to be forced to go outside by my parents, etc. I was always depressed, adults and kids bullied me, I wouldn't shower or brush my teeth sometimes. I'd cry myself to sleep almsot every day, and waking up was difficult.
About half a decade later, I've managed to hold down a retail job for years, I'm almost done with college, and I'm gonna start a nice office job soon. I don't have friends at the moment, and I am called quiet at work and school all the time. But I have no problems making appointments, calling the store to see if they sell something, or saying no to customers at work. For me, it's huge progress, I never thought I'd be independent at all. I was fully expecting to drop out of college and get fired after my freshman year.
It's fully possible to go from NEET/hikki level (or close to it) to being able to support yourself to some degree. The truth though, is that you *need* to do some form of exposure. And getting from survival mode to thriving will often take years of therapy and a medication regimen that works well for you. I've never taken meds but all my therapists have said I need them. I think if you have chronic SAD plus depression, meds will be almost required at some point, espec if you don't respond to therapy. Go to therapy if you've never tried it, but make sure you have the right mindset. You need to want to change, and you need to be prepared for the embarrassment, shame, and stress of exposure. It's always hard the first time, but eventually you'll be less awkward with things.