If you only tell people what they're doing wrong, then at some point, they'll probably start tuning out everything you say.
Being a boss is not about acting like a drill sergeant or a no-nonsense (vaguely abusive) college football coach. It's not about yelling at people, nor is it about correcting their mistakes. Those tactics may work in the short term, but they create a toxic environment with a very low ceiling for improvement.
Great bosses help their employees get better by giving them feedback that shows them a path to improvement while also demonstrating that they are valued for what they do well. Of course, mistakes need to be addressed, and some problems -- those that involve safety concerns, or poor handling of customer-facing issues, for example -- demand harsher, more immediate solutions. But most don't.
As a good manager, you can deliver constructive criticism that boosts your employees' confidence while also showing them areas they can work on. It's not a one-size-fits-all solution, but if you find a way to stay positive you can create a strong work environment where people strive to be better.
Different strokes for different folks
People have widely varying tolerances for criticism. In some cases, for example, younger workers who excelled in school may have very little, if any, experience with being told their work needs improvement. That may be a common knock on millennials, but I've found it to be true for people of all age groups.
Very few people enjoy criticism, but most are receptive to it if it's delivered the right way. I had a chance to put that into practice about six years ago when I ran a local news team comprised of three video reporters who had very different temperaments.
Reporter A was eager to please and hard to offend, making it easy to deliver criticism, but perhaps even easier to forget to praise how generally good he was.
Reporter B had a justifiably high opinion of herself, but pushed back on even minor suggestions.
Reporter C was talented, wanted to do a great job, but literally would burst into tears at the idea that anything she had done was not perfect.
Each required a different management technique, but all three were best managed by mixing various degrees of positive reinforcement with constructive criticism. It was important to not just tell them something was wrong, but show them a way to do it better. It was not simply a matter of using the compliment sandwich -- where you bookend criticisms between a couple of layers of praise -- but rather a matter of finding the right recipe for each person.
A measured approach
Since Reporter A wanted to do a good job and didn't get openly offended at criticism, he was the easiest to work with. I made sure to praise his work while kindly, but directly, sharing tips for improvement.
Reporter B did not respond well to the compliment sandwich. She liked the flattery, but rejected any direct criticism, regardless of how constructive. To advance her work, I had to make her part of the process. She was willing to put in the effort to get better, but the question of how she would do so was one that had to be answered through mutual agreement. Progress with her required a conversation; a boss who didn't do the same job as she did trying to tell her how to do it was not going to get the desired result.
Reporter C flustered me a bit because, well, you never want to make someone cry, let alone with such an benign remark as "Great piece, but next time I'd love to see a few more cutaway shots." In her case, delivering constructive criticism required first building a foundation that helped her feel secure. I needed to communicate that she was doing a good job and was not in any trouble -- but that she could make adjustments that would let her turn A work into A+ work.
You have to adapt
I've had plenty of old-school bosses who would dismiss this approach, and instead say that people need to toughen up. That might be true. Certainly, it would be lovely if everyone could just take constructive criticism constructively. Most people, though -- not just younger workers -- can't.
As a boss, you have a responsibility to know your employees and deliver criticism in a way that works for them. That's not always easy, and sometimes even a well-intentioned, well-reasoned effort will fail. There will also be employees who don't take criticism well -- constructive or otherwise. This may be because they have little interest in performing beyond minimal expectations. Or, maybe they have egos so large that, in their eyes, nothing they do could possibly have room for improvement.
In most cases, however, people will respond well to critiques and suggestions from their boss, as long as they understand the boss respects them and the criticism comes from a well-intentioned place. It's important to make criticism not about wrong versus right (though, of course, there are exceptions) but about going from good to great.
It's easy to be the boss who yells when something goes wrong, or the one who bluntly tells their staff how to do their jobs. Fear can motivate, but it's a limited tool that drives employees to find new jobs while creating an environment in which the primary motivation is not getting in trouble. Delivering personally tailored, positive, constructive criticism takes more work, but it ultimately leads your staff to higher heights.