It’s been called the greatest Grand Final in rugby league history. But the greatest moments were squeezed into a matter of seconds at the end. There’s a lesson here for investors impatient at poor market performance.

The North Queensland Cowboys, led by the inspirational Jonathan Thurston, stole a dramatic come-from-behind victory against fellow Queenslanders the Brisbane Broncos in the final moments of the 2015 NRL Grand Final on 4 October.

But just over six months earlier, near the beginning of a long season, the Cowboys had crashed to a humiliating 44-22 loss to the same team. Thurston’s team were “struggling for answers”, said media pundits, all but writing them off for the year.

For anyone despondently following the performance in recent years of the Australian equity market and of small and low relative-price stocks, in particular, the Cowboys’ experience in 2015 is a neat anecdote of how markets work.

Firstly, past performance tells us little about the future. In 2008, the year of the global financial crisis, the Australian equity market, as measured by the S&P/ASX 300 Accumulation index, fell nearly 39%. A year later, the market rebounded 38%.1

Among low-relative price stocks, the contrast was even more dramatic. In 2008, the Fama/French Australia Value Index, a barometer of that part of the market, fell 45%. The following year, it rebounded 43%.

In small company stocks, too, the turnaround was emphatic. The Dimensional Australia Small Index, a proxy for low market capitalisation stocks, fell nearly 50% in 2008, only to bounce back by nearly 66% in 2009.

But market premiums, just like rugby league teams, don’t always turn around so quickly. Indeed, realised premiums can be negative for several years in a row, as we have seen recently with low-relative price and small company stocks in Australia.

The temptation in these circumstances, to use the sporting analogy, is to get out of your seat for a while and come back when things look more “hopeful”.

But there’s no evidence that you can reliably time these premiums in the short-term. That’s because they are unpredictable and can come in short and significant bursts, just like in football. The Broncos were winning 16-12. But with seconds to spare, the Cowboys came back with a try and a drop goal in extra time to win it 17-16.

This isn’t to imply that a market turnaround is impending. But it does mean that changing your portfolio based on forecasts, instead of on your own risk tolerance, goals and needs, is a hazardous business. (Dimensional researcher Jim Davis has a detailed study on the perils of short-term tactical asset allocation here).

After their early season capitulation against the Broncos, the Cowboys were at long-odds of getting into the top eight by the end of the regular season, never mind reaching and beating the same team in the Grand Final.

The market, size and value premiums are like that, too. When they’re negative, it can test the patience of investors. We’re tempted to give up, switch channels or watch another game where the outcome seems more predictable.

But becoming a rugby league champion is a long-term grind. And success may only be finally determined in a very brief window.

As an investor, you need to take a similar approach. Stay the full “81 minutes”.