If you have to say it often, it might indicate you have trouble formulating your initial advice in a way that is acceptable to people.
Nobody likes to be told they’re wrong, so it helps to be empathetic about it. Packing your advice or instructions into a tactful and diplomatic approach doesn’t cost you much, but makes it much more likely for your advice to be accepted and implemented. And the recipient will usually end up being grateful for having avoided a mistake. They might even start to look for your and ask advice in the future. And if you keep doing that, he might even consider you a nice person or even a friend.
An arrogant and condescending approach will only do harm, even if you are factually right.
The people that don’t understand the problem usually are management, and I have to spend an exhausting time each day explaining to them why the problem exists and why it takes so long to fix it. I once was honestly telling them their meetings were a big part of the delays. Which then obviously led to more meetings on “how we can better communicate so we can have less meetings and more productive time”. I wish I was joking.