Get it and it can take you a long way.
Otago is riding it at the moment. Five wins in a row.
But momentum alone does not win games.
Execution and accuracy do. And scoring more points than the opponent, obviously.
Otago knows it has been on the rise of late. But it will take a mighty effort to get one over Wellington in the capital tonight.
Otago coach Cory Brown said the side has just treated the week normally and knows it has a job on its hands when it runs out on to Westpac Stadium.
''They're a good side, have plenty of Super rugby players and have played well this season,'' he said.
''But it is about us, really. Doing what we have to do.''
Wellington has some big men up front and will look to use its loose forwards and the likes of the departing Jeremy Thrush to get dominance of the gain line.
Brown said Wellington would come out hard at the start of the game.
''There have some big ball-runners who will try to take the ball up and they will look to go forward through them. So we've got to get up and stop them and put them on the ground.''
Otago has scored the most tries - 47 - of any team in the competition but it has also conceded plenty.
''Our attack is going really well. Guys are sticking to the plan and executing that plan really well. We've just to do the same thing when we defend.''
Those five wins in a row started with a last-minute win over Wellington and the confidence gained from that victory has grown with every win.
''Guys are playing with real belief and hopefully that will continue. We just want to play well. We are not going up there to make up the numbers.''
After losing four of its first five games, Otago has added accuracy and dash to its game.
It had threatened to do it at the start of the season but errors and some poor options got in the road.
Backs Peter Breen, Jack Wilson and Matt Faddes have all risen to the task, while up front the likes of props Hisa Sasagi and Craig Millar, and No8 Naulia Dawai, have been working hard.
But teamwork has got Otago into a playoff place, and a chance to win the championship.
Otago's success is not a secret blueprint. It has the forwards doing the basics well and the backs making the most of any space that comes their way.
Wellington was shell-shocked when it lost at the death to Otago in the game exactly a month ago and will be highly motivated to come away from the game with a different result.
If Bay of Plenty upsets Hawkes Bay and Otago wins, the championship final will be at Forsyth Barr Stadium on October 25.
Should the sides be level at fulltime tonight, 20 minutes' extra time will be played.
If that does not produce a winner, the team that scored the most tries in the game will triumph.
And if that does not work, the win goes to the regular-season winner, which was Otago, 37-36 last month.
Former All Black Zac Guildford has withdrawn from the Hawkes Bay team for its semifinal in Napier today.
Guildford pulled out because of personal reasons.
He has had alcohol-related issues in the past, but the Hawkes Bay union declined to outline the reason for his withdrawal.
Otago v Wellington
Wellington, tonight, 7.35pm
Otago: Michael Collins, Jayden Spence, Matt Faddes, Tei Walden, Jack Wilson, Peter Breen, Josh Renton, Naulia Dawai, James Lentjes, Jackson Hemopo, Tom Franklin, Blair Tweed, Hisa Sasagi, Liam Coltman (captain), Craig Millar. Reserves: Sam Anderson-Heather, Aki Seiuli, Donald Brighouse, Adam Knight, Mika Mafi, Kaide Whiting, Fletcher Smith, Tony Ensor.
Wellington: Cory Jane, Jason Woodward, Matt Proctor, Marvin Karawana, Sam McNicol, Jonny Bentley, Frae Wilson, Ardie Savea (captain), Greg Foe, Vaea Fifita, Hoani Matenga, Jeremy Thrush, Jeffery To'omaga-Allen, Leni Apisai, Reggie Goodes. Reserves: James O'Reilly, Vince Sakaria, Ben May, James Blackwell, Isaac O'Connor, Tomasi Palu, Jackson Garden-Bachop, Malo Tuitama.
Referee: Paul Williams (Taranaki).
