I've been dating my girlfriend for over 2.5 years, and at this point I know that I want to spend the rest of my life with her, but actually getting married feels very scary. It's not because I worry about her rejecting me if I propose; she tells me all the time that she wants to marry me and once I feel ready, we should get engaged. She doesn't want to pressure me too much, but at this point, she wants to be engaged sooner rather than later, even by November. And I am not scared by that, just need to be sure I'm at that point in my life.

I remember talking to a therapist about this, who told me that when he and his wife were dating, and they came to that point where they knew they were right for each other, he asked her, "so are we supposed to get engaged or something?" to which she responded something like, "no, not ready for that yet," and he said, "thank God!" and eventually they got to the point where they felt ready.

So, how do I know that I'm ready to take that next step? I'm not asking how I know she's the one. But how can I differentiate between my fear of lots of unknowns within that, vs actually not feeling like I'm in a life stage where I should be getting married? If I want to take stock of myself, how do I know that I've crossed the line from "I want to spend the rest of my life with her," to, "and I'm ready to actually go forward with that"?

TL;DR how do I know if I'm ready to marry the person I want to be with?