In this video, David Blaine explains how he was able to hold his breath for 17 minutes, beating every previous breath holding record.
He speaks about how he first tried to find a trick to create the illusion that he held his breath for so long, but then decided to actually do it. After going through months of arduous preparation, failures, and obstacles that seemed impossible to overcome, he did it.

He studied how other people hold their breaths for uncanny periods of time, the recorded limitations of the human body and how long it can be deprived of oxygen before it undergoes brain damage, and tried out multiple techniques based on scientific research. Even though outliers had shown that it was possible to survive without oxygen for long periods of time, he was still warned by doctors not to do it. However, he decided to take it all as a challenge and work hard to accomplish what others said was impossible.

What I think is even more remarkable, is that when he actually broke the record, he did it in a situation where many things didn’t go as planned. He had hoped to be completely relaxed so he would not have to spend oxygen on his muscles, but was forced to do so in order to stay submerged. He had also trained to lower his heart rate, making his metabolism go slower and therefore his heart and brain needing less oxygen to work once he slowed down his heartbeat. However, the heart monitor he was hooked up to was not planned, and the beeping of every heartbeat made him extremely nervous raising his heartbeat. He also started panicking when his body gave him signs of a heart attack. Even though his thoughts were ultimately “I’m going to fail, but I won’t quit” instead of “I can do this”, the “I won’t quit” thought kept him through it and he accomplished his goal.

Out of all that, I gathered this:

1- It’s good to prepare as much as you can
2- Even if you overcome all other obstacles, you ultimately never know what’s going to happen when you actually attempt it, and you have to get over those too, which might be even tougher
3- Sometimes it’s not about telling yourself “I can do it”, it’s about forcing yourself to keep at it and not quit.

And a healthy dose of stubbornness doesn’t hurt.