I’m almost 50, I have a good hairline, few wrinkles, and I’d probably look 40 if I shaved my nice gray beard. But I like the way I look with my beard, or more specifically, I like it more than I used to like my big round baby face. All in all, I’d rather look good than look young.
Don’t be hard on yourself. Life is a journey and maturing is a growth process. We all move in different ways and at different rates. You made it, and that’s what counts! 
I guess I’ve always looked young for my age. There were several incidents where I was assumed to be a high school student, up until my late 20s. It annoyed me a little then, but the older I get, the more I like when people assume I’m younger. Just after I turned 40, I was at a party with my then-husband, and were talking about how we had gone to Disney World to celebrate. Another guest (a friend of the host, but someone we hadn’t met before) seemed shocked and said I absolutely did not look 40.
When I was 41 and newly separated, I “met” the man who would become my second husband, through a Facebook group. When he started messaging me privately, I was fine with chatting with him about our shared interest. But when he asked how old I was, I knew what he was after, and brusquely told him “too old for you.” I had assumed, based on his Facebook pictures, that he couldn’t be older than 25. Turns out he was 32 and also looked young for his age. When I revealed that I was 41 he was surprised, as he had assumed that we were the same age. So now, as a married couple, we are 45 and 36, but I guess we look 36 and 29.
I like to attribute my youthful looks to the fact that I’ve been putting sunscreen on my face every day since I was about 18, so I don’t have too many wrinkles. Although since I’ve always been mistaken for someone younger, maybe it’s good genetics too. As for my husband, his mother says that his (late) father was often assumed to be younger as well, so I guess he has good genetics too.
People have good points, but, generally speaking, it’s rude to ask someone’s age (nor would I normally respond if they did), so there is not that much to handle.
As for downsides: when I was around 40, I dated a woman of the same age.
I’ve always looked about 10 years younger. As a telecommunications engineer, this helped me.
She could have passed for her mid 20s. But as a physician, this was a hindrance. People were always asking her if they could “speak to the doctor”. It probably didn’t help that a lot of her patients were elderly.
I worked part time at a radio station screening calls for a sports-talk call in show. The afternoon drive guy asked me how old I was. When I said 27, he looked disappointed. He said he thought he could set me up with his teenage son!
I met and married my husband when I was 34 and we both worked for a telecom installation company. We were sent to a high school to run a line to their home economics department. As we were walking through the halls with a student escort, we were stopped by a white-haired lady working as a hall monitor. The student showed her hall pass and told the monitor that she was escorting us. I was carrying a notebook with programming instructions for their phone system, and the monitor looked at me and asked if I also had a hall pass. She didn’t ask my husband!
I now have white hair, but I constantly get people asking me how old I am, and they are shocked when I say 71!
I probably look about ten years younger than my early-fifties actual age. A large part of this is due to still having a full head of brown hair, rather than thinning grey.
The only small disadvantage I can think of is on the sports field when teammates expect me to be fitter than I actually am.
I’m 70, and thanks to paternal genetics, I have no gray hair yet, so I probably would pass for being younger. Well, except for the crepe-y neck and the “age spots” on my arms. 
When I was 17, I had to deliver some documents out of town for work, and the secretary who received them took me to lunch and asked if I wanted a drink. She was surprised that I was still a teen. Of course, I was dressed professionally, so I looked older. It was an ego boost, tho.
I really don’t care - once I got past being carded, it just didn’t matter. Tho I will admit that when one of my (younger) sisters accused me of coloring my hair, I wanted to smack her. She got Mom’s hair gene and went gray in her 50s. Too bad, so sad! 
My wife went grey very early and it took lots of work on my part to convince her of the fact that she rocks the grey, now white, hair look. (Just like I rock the bald dome, even though she grieves the missing curls.)
I am what my age looks like.
I forgot to mention that a bunch of us went out to celebrate my 30th birthday, and I was the only one who got carded!
I’m 71 and my wife is two years younger and in my mind she looks 10 years younger than she is. I’ve also felt that I’ve held my age well but other than anonymously (like on a blog site) I’ve never said anything about it. Our oldest grandchild was born when I was 47 and my wife 45. One time we were in a store with her and I was standing near her when she was going to pay for something out of her own money. She was maybe 10 or so at the time. The very young cashier said to my granddaughter “did you ask your dad if it’s ok?” while glancing in my direction. I responded with words to the effect of “actually that’s grandpa”. The young lady responded with “I’m sorry”. To which I said “quite ok, that is a mistake you will NEVER have to apologize for”. I don’t know whether she caught my joke or not, but it did make me feel pretty good.
I’ve recently heard this comment “oh I had no idea you were that old!” Thanks? I guess. How old am I? it still pains me to say it out loud, ugh.