Know your purpose. Then keep reminding yourself of it whenever you have a setback or you sense your motivation flagging.

Sound a bit soft? It's what the American Marine Corps teaches recruits to do these days. They use it in the notorius endurance event, The Crucible.

It's not enough to know what we want to achieve or even how to go about it. Knowing why a goal is important helps us to carry on.

Why are you studying? Maybe, so that you can get a higher qualification, so that you can be promoted and earn a higher income, so that you can give your family more security and opportunities.

Why are you developing your team's customer service skills? Maybe, so that your customers will enjoy dealing with them, so they will get more positive feedback and be more productive, enjoy coming to work and stay with your organisation longer.

More?

Why are you going to the gym five times a week? Maybe, so that when you are fit you can enjoy family life more and be healthier and more productive at work.

Why does your organisation exist? Maybe, to provide a service or product that improves the lives of your fellow citizens.

Don't miss out on eudaimonia

Psychologists call the pleasure we get from something that helps us be our ideal selves eudaimonia. One of my long-ago psychology lecturers called it 'death-bed satisfaction', though you don't have to wait till the family is gathered around at the end to experience it.

Eudaimonia is a key to happiness or, more accurately, subjective well-being.

Ideally, your purpose should be something that would help you feel you are contributing to others. 

However you want to define it, and whatever you want to call it, think of your purpose as a guiding light to your goals and a source of mental health over a lifetime. It is.