They make those deadlines for themselves - for motivation. It is like you tell everyone that you are going to quit smoking, lose weight or whatever, and so you work harder to do what you promised not to look foolish.
Okay, and look at it like this then. Suppose I want to lose 50 pounds.
So, I setup a workout schedule, and a diet for myself.
Why should I post anything on social media at this point in time? That is way too soon to tell anyone anything.
Because, if after 3 weeks I stop working out, and go back to eating fast food... Turns out I actually gained a few pounds...
The next time I post on social media, and I haven't lost any weight, and I'm up a few. I look like a damn fool!
On the other hand...
If I made that routine, and life changes and kept to it. I'm 48 pounds in to losing the weight. Only 2 more to go. Then I post on social media "2 more pounds to go to hit my goal weight."
Then I can post pictures of before and after, and everyone is coming in like, "You are looking great buddy!" and "Way to go!"
Deadlines don't need to be "External" They can be kept "Internal" until progress is shown and you are near a goal that is within reach.
Break it down into a matrix with 4 outcomes.
Post about yes/no
Complete it yes/no
If post = yes & complete = yes then I win.
If post = yes & complete = No then I lose.
If post = no & complete = No then I draw
If post = no & complete = yes then I win.
Posting = Win & lose
Not Posting = Win & draw
Not posting is the only thing that makes sense.
This approach aligns with a risk-averse strategy, minimizing the potential negative consequences associated with public announcements that may not be met.