I like to practice being supportive and encouraging, especially when people are trying something new or sharing a lofty goal.

(It's practice because I have to work at it and screw up sometimes)

What that means is not being negative when people tell you their goal/new thing/etc.

The other day someone announced (to their social media circle) they were doing a new project on YouTube, and this was a reply:

That's . . . that's ambitious. . . best of luck with the project, and with avoiding take down notices.

It is an ambitious project, but this reads as so negative and questioning, when they could've said, "Wow! That's ambitious! I'm looking forward to it." instead of a comment that reads sarcastic and includes what they think will go wrong.

In some situations, there may be room to be "realistic", but generally that would come in conversation, not as your first reply.

I know someone who wanted to go to med school. They were hesitant to tell people because in their mid 20s people were already saying, "It's too late." And all of the "it's too late"s chipped away at that dream until they gave up ever hoping for encouragement, or for it to happen.

Sometimes it's something smaller. Someone says, "I want to learn to bake a pie." And you, an experienced pie baker who still struggles, think of all the difficulties with learning to bake a pie, but instead of listing them! You say, "Awesome! Let me know if you need advice!"

Anyway do what you want. This is just my little contribution to positivity in the world that I'd love to see more of.