I'm in my 30s (I apologize for being vague; it's a privacy thing, mostly, due to the vultures we get afflicted with here) so I really understand feeling older than the norm when it comes to transitioning. For me, however, I stopped having relationships in my mid-later 20s. It was dysphoria-related, as I was having more and more trouble connecting with a female body and I could not abide being in a relationship with someone who was reading me as a female. This got more extreme, where I was pushing away even friends except for one stubborn one who refused to give up. In other words, I didn't run into the issue of relationship/kids getting in my way when I finally transitioned. Job-wise, I retired from my previous line of work and went back to college since I had never gotten any kind of degree and I wanted to accomplish that.
At this point, transition has been great for me; I no longer feel like I'm just alone and waiting to die. I am surrounded by supportive friends and I feel attached to my body again. I no longer feel like hiding in a dark house, hoping I'll drop dead so I can be at peace. I know that sounds ridiculous and morbid but it's where I was before I finally came to terms with being trans. I'd been denying it for so long and fighting against it and making myself endlessly miserable.
Kind of ridiculously, my big hurdle in all this has been how youthful I look. Youthful is good but when I say this I mean I looked like jailbait. Prior to transition people read me as being about 23, which is fine when you're in your 30s. After transition people were reading me as 14-16, which is NOT FINE when you're in your 30s. At college it's okay because I just blend in. Elsewhere, it's honestly awful. Several times now, when I've been out with friends, others have addressed my friends either as my parents (oh my god) or just talked to them over me because they assumed that I was a kid hanging out with grown ups. Not to mention, guys I might be interested in (who tend to be in their mid 30s to mid 40s) feel uneasy flirting with me because it makes them feel like creepsters.