Make it universal

People will relate more to your stories and content if you appear to be more like they are. If you graduated Harvard, finish marathons in less than three hours, and spend your Summers in Paris your audience will have a hard time relating to you...and therefore relating to your points.

As the great speaking coach Craig Valentine says, "When you build yourself up you let your audience down." Don't be the hero of your own story. Sure you are speaking to them about something you know...and something you would like for them to know...but if you build yourself up you let them down. 

Instead talk about your own faults and failures. If you struggled early on they can relate because they struggle too. If you took a long time to learn something they will related because sometimes it takes a long time for them to learn also. The more like them you are...the more they will ready to receive your message.

Make it universal. If you do bring up your marathon training make the struggles universal. Say something like, "Once I signed up for my first marathon I suddenly found myself paralyzed with fear. Do you ever do that? Do you ever suddenly have a crisis of confidence? Have you ever been terrified of failure and having everyone find out you are an imposter?" The audience will relate to that message and get your point. 

A great article on this here:
http://www.bakadesuyo.com/2012/06/are-stories-we-can-relate-to-the-key-to-learn/