In honour of the 20 year anniversary of the Agile Manifesto, each monthly blog this year will focus on one of the twelve principles.
"Agile processes promote sustainable development. The sponsors, developers, and users should be able to maintain a constant pace indefinitely."
The underlying message behind this principle is really around respect. Instead of forcing people to work crazy amounts of overtime to adhere to deadlines they didn't agree to in the first place, let's look at what we can accomplish (in a sprint for example) and work towards that.
Too many times, teams are burnt out. They just finished putting out the latest fire and now they have to face the next one. Moral is low and turnover becomes the norm. This is not the environment we want to create.
Additionally, unsustainable development doesn't allow us to forecast. This approach doesn't give us the luxury of being able to predict what we can accomplish. So somebody comes up with fictitious deadlines and the vicious cycle repeats itself.
There are times where we need teams to put in extra time. The theme here is that overtime should not be the norm. If we treat people with respect, they'll likely produce better results. So we should start trusting our teams.