Sometimes it takes just a touch of youthful, untamed pace and panache to quite transform the feeling in a football changing room.
Manchester United boss Louis van Gaal's unusually upbeat tones after the latest match-winning heroics of 18-year-old Marcus Rashford in the Premier League derby suggested that the Dutchman had discovered his own young mood-changer.
"Their (the players) reaction was fantastic to see in the dressing room," Van Gaal enthused, after Rashford's lovely 16th minute goal in his first game against Manchester City sealed what the manager seemed to feel was a victory worth more than three points.
"We fight every match of course but now we have a big result. It's a long time since we have won here and it's fantastic for the fans too."
The provider was again young Rashford, who some pundits had been suggesting perhaps needed a break after his startling introduction to the big-time had seen him score twice in both his debut in the Europa League against Midtjylland and on his Premier League bow against Arsenal.
Yet the local lad's appetite for 'firsts', it turned out, is not sated. Having become United's youngest-ever scorer in European competition, he now becomes, at 18 years 141 days, the youngest to score in the derby in the Premier League era.
It was no ordinary goal, either, as he sped past City defender Martin Demichelis -- making the Argentine, as Van Gaal noted of his old Bayern Munich defender, look every one of his 35 years -- before side-footing coolly past Joe Hart.
United should have been awarded a penalty too just before halftime when Demichelis, finding him too difficult to handle, got away with bundling over Rashford in the box.
"It is so refreshing to see a young kid like Marcus run at defenders like that," said United's admiring England defender Chris Smalling, noting that he would not fancy facing him as a centre-back.
"It was a great goal from Marcus, an unbelievable finish," added Michael Carrick, giving an indication of the impact the youngster's contributions had on his teammates once again.
United needed a boost after their exit from the Europa League against Liverpool on Thursday and to hold on so gamely to their early lead while so obviously tiring and under considerable City pressure at the Etihad provided just that.
Van Gaal reckoned he was "a very proud manager" after a performance that put United sixth, behind West Ham United on goal difference and just a point behind fourth-placed City in the increasingly tough battle to earn Champions League places.
Yet the likelihood of Rashford playing a key role in that final push was obvious after Van Gaal declared: "He is a real striker and that's why I let him stay in that position.
"He can score goals but he's also an attacking point and runs the channels. I like him very much. He's just 18 so we have to wait and see how consistent he is."