Anna and Christine met at a creative writing evening class two years ago. Both in their late thirties, they lived near each other and shared a common dream of writing a novel. Soon they had established a weekly writing date at a local coffee shop. They would chat for a few minutes, then work on their respective books for an agreed time slot, then reward themselves with cake.

Yet as the weeks passed, Christine began cancelling the sessions, or turning up late. And if she did appear, she’d often want to spend more time chatting than writing.

Fast forward to today and it’s no surprise that Anna is the one with the finished manuscript while Christine has yet to get further than the opening chapter. Kelly McGonigal, health psychologist at Stanford University and author of Maximum Willpower, recognises this scenario. All too often, in order to achieve the things we really want to, what is required is not so much natural talent or desire, but good old-fashioned perseverance.

McGonigal teaches a course  called The Science Of Willpower, which focuses on helping people to harness perseverance in order to achieve what they want. She divides willpower into three separate categories. ‘I will’ (something we aim to do more of), ‘I won’t’ (giving up a sticky habit), and ‘I want’ (a long-term goal). This classification is based on studies by neuroscientists identifying that the prefrontal cortex (the part of the brain behind the forehead and eyes) is set up to control what we think, feel, and do.

The left part corresponds to ‘I will’ (sticking to boring, difficult tasks), and the right-hand bit controls ‘I won’t’ (going out with my mates every night).

It’s the lower-middle part that controls ‘I want’ and tracks long-term goals and desires. It’s worth noting that temporary states such as getting drunk inhibit this third part. In other words, downing the chardonnay drains your willpower.

Once you understand how the brain processes these different aspects, it’s a lot easier to harness willpower. The key, says McGonigal, is to reframe your intentions by turning so-called ‘resistant thoughts’, such as  ‘I won’t spend hours on Facebook’, into ‘towards’ goals, such as ‘I will spend my free time researching new work opportunities.’

One of the biggest revelations in Willpower: Rediscovering Our Greatest Strength by Roy F Baumeister and John Tierney is that neuroscientists have been able to show that we have a finite supply of willpower. During any given day it can easily get used up. ‘Acting on impulse doesn’t have an impact on willpower,’ says Baumeister. ‘But anything we exert mental control over does.’

Anyone determined to change their life on many levels has to proceed step by step. ‘Someone trying to make two changes at once will find it harder as we have one stock of willpower,’ says Baumeister. He recommends starting with the easier of the two to change and taking things one goal at a time. Psychologists have also identified that willpower is infectious. If we surround ourselves with people who display a high level of commitment and self-control, it’s likely to rub off on us.

So-called ‘goal contagion’ is highest among our closest connections. If your friends aren’t interested in making changes, it’s harder to make changes yourself. Baumeister’s studies both in Europe and the US confirm that people with high willpower have fewer inner conflicts. This is because they gravitate to friends and partners who support them.

‘Although in one study we found that people with high self-control can be attracted romantically to opposites with no self-control when dating, they tend to marry someone similar. Best friends tend both to be one or the other from the outset.’ For anyone who recognises that they have low self-control, hooking up with a partner or a new friend with high self-control would be beneficial. ‘Someone with no willpower is definitely better off with a person with high self-control,’ says Baumeister.

‘If you have close family or a partner or friends likely to derail you, it’s important to get them on board and explain that your goals will benefit them too,’ says McGonigal. ‘Otherwise you have to develop the conviction to break through relationships that sabotage your wellbeing. Disengage a little. Be willing to make a choice about who you spend time with and who you allow to be in your head dictating what’s right for you and what isn’t. Strengthen your own convictions and stop getting approval from others.’

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Read Do you have enough self-discipline? on LifeLabs