Good thread. This is something I have been struggling with, so it was interesting to read people's thoughts on it.
I have never really been into social media, but recently got an Instagram account and set up a website/blog. Having earned my pro card a few months ago, I feel like it is an obligation to post stuff about my training and racing.
They say that when you stop seeing ways you can improve, you will stop improving, so I usually try to include both positives and negatives. But if the positive is that you won the race, then I guess any negatives (like not achieving a time goal) can easily come across as a humble brag.
On the other hand, if I have a race where I am really struggling, I want to be honest about that, too. As others have mentioned, it feels really awkward when people say "OMG you are amazing" when you know you should have been able to go faster. The Augusta 70.3 last weekend was a great example. I was 13th out of 14 pros, and also got beaten by a handful of age groupers. My run split was eleven minutes slower than my run PR. It is tough to figure out how to write about that, acknowleging the disappointments, while still realizing that the vast majority of participants would happy to trade times with me.
One thing I'm trying to do is list specifics: "I was thrilled with my swim, but bonked on the run", instead of making a blanket statement about whether it was a good race or not.
Just learning the ropes of the social media stuff, so it's useful to see people's thoughts on what is and isn't good to say about race results.
If you find yourself thinking "What if I can't", instead think "What if I can!"