The Power Of Why 

If I asked you to walk bare foot over a bed of broken glass you probably wouldn’t do it. If I had a loved one, like your brother, daughter or mother at gun point and said I would kill them if you failed, you’d probably finish the challenge. 
“Why” can be a VERY powerful motivator. That is an extreme example, I grant you. But it illustrates my point. “Why” provides purpose, context, drive, determination and resilience. Why can be the most powerful force in the world. It can create a man possessed. It can create a Woman not to be played with. It can create heroes and it can defeat overwhelming odds. Make no mistake “why” is a powerful thing. 
If your why is strong enough, you will be able to produce greater efforts, for longer periods of time, against greater challenges than if you don’t have a great connection with why you’re doing things. 
It can be hard to convince yourself to work harder instead of chill. It’s not natural to push yourself through pain instead of run from it. But a strong enough why will fuel you with the resilience and strength you need to get the job done. 
Nick Dunn described this to me after he won his age group in the triathlon world championships last year in London. 
He was feeling the pinch on the run. Years of training came down to this one day and he was now in the lead, with less than 1K to go. Knowing he was up against a strong field, knowing that if he let up it might all be for silver. His lungs burning, his legs heavy, Nick told me how he thought about the brutal prowler drills he had endured. The 15 sessions per week he had battled through. The nausea and pain of every session of repeats. He thought about his wife giving birth just days before. The thought of all that being for silver was more painful than simply pushing a little harder for just a few more minutes. As a result of his toughness and his connection with his why, he was able to win by 35 seconds. 
I have seen countless other situations where a strong connection with “why” has given trainees the strength to push through when they wanted to quit. 
If you know that the pain of not reaching your goals outweighs the pain of a tough training session you can persevere, and dominate your inclinations to quit. 
This is true not just in the gym, but in all areas of life. A business consultant I had the pleasure of working with this year told me that on the days he doesn’t want to work, the days where he could easily relax at home instead of reach out to new clients, he thinks of not being able to financially look after his mother in a few years when she retires. That pain would be much stronger than the pain of picking up the phone and calling a lead. 
If you want to achieve great things in training, understanding why you want it can be a powerful weapon in your arsenal. Think deeply about why you want what you want. Then connect with that why when you need motivation to crush it.