The unpredictability of sport is in many ways its greatest attraction, and unforgettable come-from-behind victories are especially captivating.
During these epic comebacks, one team or athlete is generally said to have captured or capitalised on one of sport's great intangibles: momentum.
But what is momentum in a sporting sense?
Why 'the zone' and 'flow state' are key
Psychological momentum in sport refers to a functional overlap between two theoretical concepts: the individual zone of optimal functioning and flow.
In other words, these are known as athletes being "in the zone" and "in a flow state".
Getting "in the zone" is where an athlete's perceived level of effort and emotional intensity strike a perfect balance that leads the athlete to achieving optimal performance.
Similarly, achieving a "flow state" is where athletes experience an almost effortless performance with a strong sense of control over their movements.
Think of momentum as when an athlete or team is able to dominate an opponent with remarkable concentration and control, seemingly mastering a game or series of plays in an effortless manner.
This may seem like a random phenomenon, but developing momentum in sport can be understood through a few psychological concepts regularly applied in the heat of the moment by some of our top athletes.
Unsurprisingly, practice is also important
As with all sporting performance, practice indeed makes perfect.
So while the facets of momentum won't happen overnight, it's important to routinely embed psychological training within and around a sporting season - and this psychological edge is often what sets the experts apart from the novices.
For young and aspiring athletes, dominant reigns from our favourite athlete or sporting teams can be inspiring. But what we see is much like an iceberg - we don't often see the preparation beneath the surface.
Learning to fail and coping with unexpected events, and applying those lessons to future improvements, is one of many strategies to develop mental and emotional resilience.
Arguably just as important is managing different sources of pressure within and beyond our control.
So as much as we'd like to think Roger Federer's backhand is indeed effortless, the sporting statistics and accompanying research shows that achieving these "in the flow" or "in the zone" states are actually amassed over the course of a career - and some are fortunate enough to capitalise on that to build upon that momentum.
Momentum within games and across seasons
To clarify, this concept of psychological momentum isn't a physics lesson providing an overview of Newton's momentum.
While momentum indeed represents a driving force that carries motion and influence, in sports it is the combined effect of positive sporting performances and how athletes are able to control their mental state in those key sporting moments.
This can be altered by internal consistency or external disruptions, demonstrating the dynamic nature of momentum in sport.
What's intriguing is that momentum in sports can be classified within a match or event - think Collingwood's incredible recent history of comeback victories in the AFL - and across a season as a whole (such as the Australian men's Test cricket team setting world records for consecutive wins in the late 1990s and early 2000s).
Across a season, you can consider momentum in sports to be an example of success breeding success - suggesting to athletes that they have the capacity to make the most of victories early in a season and leverage that motivation to do well in subsequent events.
This confidence can be seen in individuals and teams - doing well makes us think that since it's been done before, we're capable of doing it again.
And when you secure successive wins as a team, the athletes will start to rationalise that what they're doing together is working. That will begin to develop further cohesion and provide an overall boost to morale.
Even within a single match, fans can see a team creating more situations that will lead to more scoring opportunities increases the likelihood of that team earning a victory.
Regularly creating these opportunities, especially early in the game, can be the difference between winning and losing. This could be due to the players on the losing team beginning to doubt themselves or struggle to deal with their own frustrations as they encounter more setbacks contributing to the loss.
Essentially when an athlete or team has momentum, it's more than just being confident: athletes have to also manage their internal responses (for example, level of frustration) and how they respond outwardly to what happens during a live match while making clutch decisions at the right time.
How to halt an opponent's momentum
As with all good things, there is indeed some risk with "riding the wave" of a winning streak - complacency and overconfidence can creep into the team or athlete's preparedness and can make way for some remarkable stories of others infiltrating (and ultimately breaking through) that momentum.
If you're in the thick of a losing streak or a game is slipping away, athletes and coaches must find ways of disrupting the momentum of the winning team.
This might be strategic discussions such as taking a timeout or, in cricket, switching the bowling line up.
These tactics can disrupt the opposing team's flow.
Understanding the complex nature of momentum is crucial for helping athletes and teams refocus on what is actually within their control and how they can individually build their sporting confidence over time to perform well under pressure.
The ability to handle setbacks and the opposing team's skill in capitalising on these moments can be the deciding factor between winning and losing.