"Everyone wants to play every game, no matter who you are," he said yesterday.
"Growing up it's what you want to do and it's never nice missing out. But the reality is if you are playing all three forms you physically can't play every game in a calendar year.
"So as hard as it is, you have to accept it's for the best for the team."
There's also the question of longevity.
Pacing oneself can extend a career and prevent burnout or, in some cases, injury.
In this of all seasons, with the World Cup played in February and March, there is a need to have all players at their optimum at the right time.
"It is important to rest when you can, and what you do between games is also very important," Southee said.
"I had a good conditioning window leading up to the season, which was good. We have the luxury where we can afford to rotate bowlers and give others a go.
"We are all competitive people and that adds an edge to training and games.
"You've got to make every game count and if someone's breathing down your neck it's healthy to have."
Southee had an uncomfortable moment in the nets yesterday, struck first ball in a tender place by strength and conditioning coach Chris Donaldson.
A touch embarrassing, especially when caught on film.
Kyle Mills and possibly Trent Boult, who led the New Zealand attack on Tuesday, are likely to sit today's game out.
The one interesting choice could be whether to play both spinners, Dan Vettori and Nathan McCullum, or use a third specialist seamer, the intriguing Matt Henry or left-armer Boult.
However, New Zealand's primary focus since the first game is more likely to be on batting.
On Tuesday, it was ordinary save wicketkeeper Luke Ronchi's rousing 99, his best ODI innings and one which could in time come to be seen as a pivotal point in his summer with the bat.
As for South Africa, their cards are close to the chest, but they may opt for the same XI with the exception of introducing hard-hitting David Miller, who picked up the flu on the flight to New Zealand, for Rilee Rossouw.
Test captain and senior batsman Hashim Amla, slower than usual with his run rate en route to 38 on Tuesday, said the key adjustment for batsmen in ODIs is knuckling down if pitch conditions demand it, rather than automatically going hard at the ball from the start.
"The tendency, especially with the advent of T20, is to try to score quickly up front," Amla said.
"If you don't have a wicket that allows that, the biggest adjustment is to bite your tongue a little and try and block a few dot balls."
NZ v S Africa
2nd ODI, Mt Maunganui 10.30am today
New Zealand: (from) Brendon McCullum (c), Martin Guptill, Jimmy Neesham, Dean Brownlie, Tom Latham, Corey Anderson, Luke Ronchi, Dan Vettori, Nathan McCullum, Tim Southee, Trent Boult, Kyle Mills, Matt Henry.
South Africa: (from) AB de Villiers (c), Hashim Amla, Quinton de Kock, Faf du Plessis, Rilee Rossouw, David Miller, JP Duminy, Ryan McLaren, Vernon Philander, Dale Steyn, Wayne Parnell, Morne Morkel, Imran Tahir, Aaron Phangiso, Kyle Abbott.
3 Things NZ must do in second ODI at the Mount today
Keep their heads up
If things go wrong in the rest of the South African series. It's a long summer, with piles of cricket to come so no need to push the panic button at this stage, but...
Maintain standards
Notably with the bat. Game one was a hiccup, but consistently good quality performances are important with one eye on the World Cup early next year.
Take their opportunities
October is early doors in a marathon season, but this is no time to take the eye off the ball. A win on the pitch is also a victory for mind games ahead of the cup.
