The next time you've told yourself you'll go for a run, but you really don't feel like actually getting up and going, have a think about 35-year-old Sean Conway.
Because there's pushing your body to new limits...and then there's cycling over 3,000 miles, running 800 miles, and swimming 100 miles. Which is exactly what Sean, from Cheltenham, is currently doing, as he attempts the world's longest triathlon.
After 36 days of cycling and 31 days of running, he's now made it to the swim. Incredibly, throughout the triathlon so far he's only had one day off, when he had a knee injury.
And the ridiculously impressive challenge has gained him a lot of fans on social media, thanks to his hashtag #GoSeanGo.
"All the support I'm getting from the general public has been amazing," says Sean. "Doing these solo things it can get kind of lonely but people are coming and finding me and saying 'hi'.
"Twitter, Instagram and Facebook; between the three of them that keeps me sane".
After all, Sean is having to overcome major challenges - he needs to eat thousands of calories a day and is also trying to do the triathlon self-supported, so he can't take things like camping equipment and food along with him.
Which does mean he's stayed in some pretty cool places along his route.
But the last leg of the triathlon is bringing up some fresh challenges for Sean - including the fact his raft which he's dragging behind him on the swim is currently leaking.
"I've got to swim through the solent, the busiest shipping lane in the world, and that's a real worry - not to mention the hours and hours I'm spending in cold water", says Sean.
"There's two tides a day and you can only swim with the tides. So I do 3/4 hours in the morning and 3/4 hours in the afternoon."
He admitted that he's struggled "almost every day" of the triathlon, but added that the swimming is particularly miserable.
"At least with running and cycling you meet people and see different things. At the minute I look at water and then sky, water and then sky, every day.
However, he described his absolute worst day so far - and it's when he was cycling.
"There was that day in April when it snowed in Scotland. It suddenly came down and I just wasn't prepared for that - cycling in the middle of nowhere with summer kit on, hail coming down, and it was 5 degrees.
"It felt like I was being shot in the face with shotgun pellets."
Meanwhile, the effect this challenge is having on Sean's body is obviously huge and he says eating enough calories is really tough.
"Today was particularly difficult because I happened to finish my swim two-and-a-half hour round trip from anywhere with food so I had to walk for two-and-a-half hours, without any food.
"I'm really skinny, I've got no body fat any more, no energy. I'm not really getting much more than 4/5 hours sleep at one go at the moment, I get up at 3.55 in the morning, to get in the water at 4.30 and then I swim until about 7.30/8, then I have to wait until the second tide in the afternoon. I'm just generally exhausted."
"I've done similar challenges but this is me stepping up my game - I believe this is the world's longest triathlon. I just wanted to do something a bit harder than before. But maybe not this hard actually.
"I think I've jumped up a step too far really."
But Sean says he's motivated by the thought of inspiring people to be active and explore Britain, especially because the Discovery Channel is filming the triathlon for a three-part documentary series, which is scheduled to be broadcast on the channel in the UK and Ireland later this year.
"I wanted to do one more adventure in Britain, I wanted to explore the coastline and I wanted to inspire people to get outside in Britain. And hopefully through the Discovery Channel I can reach more people and inspire more people."
You can join in with tracking Sean's progress at DiscoveryUK.com.