I agree with what the other posters have said.
From what I have noticed, your age group (late teens to early twenties) is where adult aspies seem to have the worst bump in the road. This isn't true for everyone- it's just a generalization. You don't have the same structured systems in place and you have to figure out how to deal with employment, friendships, romance, and daily living on your own. How do you want these things to be and how do you make it happen for yourself, you know? It's not easy. Not for anyone, but it's harder if you're a social minority such as a person on the autism spectrum.
If your mom is neurotypical, she could be seeing this time in your life as exciting and the best years you will ever have. Some great things may indeed happen to you in the next few years, but it may not be the kind of experience that you will always look back on fondly and wish you could do again. Your life will probably get better each day from here, incrementally, not be a roller coaster. *I* think that's a better overall life, but it can be a little difficult for some people to understand.
So although I agree that she's probably just trying to be positive and supportive, I think it's really important for her to understand where you're coming from.