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Some last as long as the average diet or a well-intentioned New Year's resolution.
For Greg Henderson it lasted about 18 months. He has emerged from what was a relatively brief hiatus and is once again chasing glory on the world stage.
The 42-year-old former professional cyclist is targeting the masters track world championships in 2021.
And he is also back studying at university.
Why? Well, life has changed, circumstances have changed and he still has the hunger to compete and learn.
It is also keeping him focused during a tough time in his life. His marriage to former Australian Olympian Katie Mactier ended last year.
The couple have two children - Charlie (9) and Lachie (6) - and it is hard not to see them each day.
"For me I need goals and I've been like that my whole life," Henderson said.
"I need direction, so with university I have a lecture at 9, 11 and 2 and I know what I'm doing. And then I have time to do two hours' training.
"I just love structure and I guess I've always worked like that."
Henderson got the idea to return to the track while at the nationals in Cambridge last month. It fired his competitive spirit.
"I looked at the competitors who race in my age group and I thought I want to have a crack at it and get another world title.
"I'd love another rainbow jersey, so I thought, well, here is an opportunity."
There was no thought to returning to road racing, though.
"No one part of my body wants to do that anymore. I've had years of that. With track racing... it is about your power and your speed and tactical knowledge, which has actually always been one of my strengths.
"So that is the goal. To get a rainbow jersey in a couple of years."
When Henderson retired he wrote on his website he had achieved much more than he could have imagined when he was a child speeding around Otago's BMX tracks.
His list of achievements underscore that point. His first major win came on the track at national level in 1996.
Two years later he claimed bronze medals at the Kuala Lumpur Commonwealth Games in the points race and teams pursuit.
In Manchester four years later he upgraded to gold in the points race and bagged another bronze in the teams pursuit.
Success on the world stage was waiting as well. He took silver in the madison at the 2003 track world championships, and gold in the 15km scratch race the following year.
That raw speed proved more than useful when he switched his focus to road racing. He developed a reputation as an uncompromising lead-out man, first at Team Sky and then for Lotto-Soudal from 2012 where his partnership with German Andre Greipel produced many, many wins.
Henderson competed in the Tour de France five times which was a major achievement. He also claimed a stage win on the Vuelta a Espana and two stage wins on the Paris-Nice.
These days he works as a cycling coach. He is also an ambassador for Evo Cycles in Dunedin and Giant Bicycles New Zealand. He is also kept busy studying at the University of Otago.
"Turns out I only needed a couple of papers to finish my BSc in exercise science, so I'm doing that basically.
"Again it is another boxed ticked when you are a coach with a bachelor of science. And I'm really, really enjoying it.
"But honestly, when I went back university, it had been nearly 20 years. I got to my first lecture with my note book and pen and I'm the only one with a note book and pen."