When I was doing Ironman triathlons, I was a member of Endurance Nation, an online community of triathletes led by a couple of coaches. The bedrock of Endurance Nation's training for an Ironman is what they refer to as the Four Keys of Race Execution, where the premise is that driving your body through a self-propelled 140.6 miles is simply too big a problem to solve without a strategy and an approach to solving a really big problem - because as it turns out, swimming 2.4 miles, cycling 112 miles, and then running 26.2 miles, all within 17 hours, is a really big problem.
But before too long, I started realizing that the four keys are applicable to approaching big challenges in general, not just for Ironman triathlons.
Execution (X) -
The box (B)
The line (/)
The one thing (1)
Execution
As a kid, I used to think that all I needed was a great idea, and I could become rich - and I'm sure I'm not alone in that regard. However, I eventually came to learn that an idea itself is cheap and just about worthless - the real value is the ability to execute. Being able to execute is so important that seemingly bad ideas (like inviting strangers to sleep in your spare bed) have become the basis for a company (AirBnB) now worth over 100 billion USD, simply because someone figured out how to execute on the idea in a way that was appealing. Execution doesn't have to be being able to throw the long ball 80 yds for an amazing touch down. It's exciting when that happens, but it can simply be picking up the ball and moving it a few yards. As long as there is big picture directional vision, and the needle is being moved, those inches add up over time. Execution - being able to think critically about the challenge or problem to be solved, and being able to move the needle in a productive way - is what gets results.
There are certain things we can control, and there are certain things we cannot control. When faced with a major challenge, it is critical to evaluate and know what we can control (and therefore what we should expend mental energy on), and what we cannot (and therefore what is not worth a second thought).
For example, if I am working with a customer, and they are evaluating my proposed solution and a competing solution - I can control how my solution is presented, I can control the messaging of how my solution addresses their needs/concerns, and I can control whether my relationship with the customer is full of positive interactions or not. However, I cannot control what the competing solution features are, and I can't control the messaging of the competition when I'm not around (however, if I know what the messaging may be, I can control my response to the customer around said messaging).
Control what is in your box and within your sphere of influence, and don't get overly concerned about what is outside of your control.
The Line
At some point, things are just going to get hard. Challenges wouldn't be big if they didn't have a point where things become a grind. The first thing is to recognize that it's going to happen. The second thing is to make decisions from the start to push that line back as far as possible. Usually this comes down to preparation - if I know a certain obstacle is going to pop up in the future, I can make decisions well ahead of time to either minimize the discomfort, or at least prepare for it in some way to maximize my chances of success.
Donald Rumsfeld caught a lot of flak back in the day for talking about known unknowns and unknown unknowns. While known knowns and known unknowns sounds goofy, he was actually spot-on. If we prepare for the known unknowns ('surprises' that, with some forethought, we can anticipate), we push the line back, and we reserve mental bandwidth and attention (a resource more precious than time) for dealing with unknown unknowns (true surprises) as they come up. Things will get difficult. Know they will get difficult, and do what you can to push that line back as far as possible
The one thing
If we are taking on a big challenge, we are doing so because we are motivated by some sort of why. We want to set a good example, we are raising money for some cause, we are furthering our career, etc. However, humans can be very good as justifying secondary outcomes that are easier, especially when we are in the grind of a situation and just want out, or to be done, or move on to the next thing.
Therefore, it's important to understand the true reason for doing something, and being honest with yourself in exploring and understanding your motivations. Are you doing something because it is expected of you from someone else, or are you intrinsically motivated? One can accomplish things in the case of the former, but people can push themselves a lot further in the case of the latter. Many times there are multiple factors that play into a decision to take on a big challenge - it's important to keep those factors and motivators in mind, because when things get tough, a single reason may not be enough to continue pushing and pursuing to the final end goal.
What is the primary motivation for taking on the challenge that will help keep you on track when things get tough? And... it doesn't hurt to have multiple 'one things'.
Big challenges are hard. They require planning, they require dedication, they require discipline, they require patience - and that is all a lot of work. But, with the right framework and approach, big problems are manageable, and they are achievable.