Andrew Steele, 23, from Manchester, is competing for Great Britain in the 400m and 4x400m relay.
After a crazy few days, Iím once again sitting in my hotel room and thinking back over the emotional rollercoaster that has been the past three days.
This sport provides you with the highest highs, but unfortunately also the lowest lows - and I have just experienced both.
At 4:30am on Monday I arose to compete in the first of a possible three rounds of the menís 400m, here in Beijing. The moment I got out of bed, I knew it would be a good day; I felt nervous but in control.
At this level, the distinction between the winners and the also-rans is the ability to execute and stay cool under the greatest pressure.
I knew if I stood any chance of progressing to the semi-final, I would have to run the fastest I had ever ran in my life, this is not an easy fact to face I assure you!
My warm-up felt great, and eventually the time came for me to enter ďfinal-callĒ. This is the small room where you report before your event, where they plonk you down right next to all your other competitors Ė as if you werenít nervous enough already!
Twenty minutes later we emerged into the wonder that is the Birdís Nest stadium which, much to my surprise, was full to the rafters with 91,000 people and the atmosphere was incredible.
During my race, I felt strong and relaxed and with just under 100m to go I found myself in the lead with no challenge. I crossed the line to see the big clock stop at 44.94 seconds - a huge personal best and something of a landmark as far as 400m times go.
This is the first time I have run under 45 seconds, so I am really thrilled with my performance Ė plus it felt easy! Cue happinessÖ
I spent the rest of the day relaxing, and looking forward to having a lie-in the following morning. The semi-final was not until 9.45pm the following night.
This was not a good race for me. I felt a world away from the athlete that ran the heat the previous day and after 200m I wasnít involved in the race at all.
I tried to come home strong but I just didnít have anything left. I finished last in a slow time of 45.5 seconds.
I canít begin to describe the disappointment I felt - the high of the previous day had just been all but erased by my terrible performance in the semi-final.
I should have made the final here, but I didnít run my race right and I didnít keep my cool when it mattered. This was my own fault, and something that Iíll now work on and correct for the future. Cue despair!
After a long dark night of the soul, I have now brushed off Tuesdayís disappointment and Iím really looking forward to the relay on Friday.
Since my race, I have been inspired by Christine Ohuruoguís amazing run for gold in the womenís 400m and also by Usain Boltís unbelievable world record in the 200m.
Team GB are having an amazing Olympics, and so far I have experienced the full cross-section of what the Olympics have to offer. It really is such hard work mentally, but I would rather experience the lowest low, while chasing the ultimate high, than live a normal quiet life and experience neither.
So watch out for the menís 4 x 400m relay heat Ė 1310 BST on Friday - and shout at the TV!
Previous 606 entries from Andrew Steele:
In the eye of the storm