Novlene Williams-Mills memorably bounced back from serious health problems to win the Diamond Race in her event last year.
Here the Jamaican 400m runner talks us through some of the best things in her world.
My best friend in athletics
I've always been very close to Kenia Sinclair (Jamaica's 2006 world indoor 800m silver medallist). We went to school together and we were coached by the same coach. We go way back.
I'm also really good friends with David Oliver. We trained for a period of time together. David is similar to me. He is very blunt and not afraid to say what is on his mind and that's what I like about him and, believe it or not, we were born two days apart!
My best achievement in athletics
With everything that was thrown at me (with a diagnosis of breast cancer in 2012) to come back and enjoy my best ever year, become world number one and Diamond League champion in 2014 was a big achievement for me. I started out 2014 saying if this doesn't go well then this will be the end. I'm so happy it turned out in my favour.
My greatest disappointment
The 2008 Olympics, when I didn’t make the 400m final. I was in good shape, I don’t know what happened, it was just one of those days when I ran badly. It was a big disappointment for me because I knew I was ready to run. Sometimes things don’t go as planned.
My best rival
Since I’ve been out of college, I probably have two, Sanya Richards-Ross (2012 Olympic champion) and Christine Ohuruogu (2008 Olympic champion). Each athlete brings something different.
You know Sanya is going to go out and try to control the race. With Christine, if you are not strong enough to finish the race then she will get you at the end. They are two different athletes who bring something different to the table.
The best athlete I've ever seen
It has got to be Usain Bolt. When you are an athlete who can not only win two or three championship events but also do so in world record times, then that is unbelievable.
My best piece of advice
Early in my career, I was coached by my college coach, Tom Jones, who really got to know me as an athlete. Back then I lacked confidence and did not believe times such as 49 seconds for the 400m were possible, but he always believed in me and said you have to believe in yourself.
He helped my focus in training and I guess he saw something in me that I didn't see in myself back then. Tom sadly passed away in 2007.
My greatest indulgence
For me, I like to spend time with my husband on the sofa watching TV. This year I've been watching Homeland and The Blacklist.
My best pre-competition music
I’m a fan of gospel music. I find it inspiring to listen to when I'm preparing for a race. Last year I loved listening to William Murphy, This is My Season. The song made me think that it was a season of grace and favour, of mercy for me; that it was my time which God has given me back to show other people I am still alive.
My favourite venue
I love the Olympic Stadium in Rome. Maybe it is because of the history, or maybe it is because it is the place where I ran my first sub-50 second run but I have a little connection there. It is a great facility. Another one would be Shanghai. I really like the fact the athletes' hotel is based at the stadium, so I have very easy access to the track.
My greatest regret
I don’t have any regrets. For me, everything in life happens for a reason.
My best achievement outside of athletics
My husband, Jameel. He has seen me at my highest and lowest. He has been there when my coach and my sister died, and he was there when I had cancer. For him to support me through all of that has been amazing.
Steve Landells for the IAAF