Is this a good idea or a bad idea?
Is this a good deal or a bad deal?
Is this a good job or a bad job?
Is she a good girlfriend or a bad girlfriend?
No one knows.
And the only way to know whether it's good or bad is to do it.
To work on that idea.
To sign that deal.
To take that job...
So how can you know in advance whether or not something is really worth it?
You just can't.
The problem is that in the cases that really matter, the cases that are just way too complex, there's no way to know in advance whether or not it's going to be worth it.
The only way to figure it out is to do it.
And the more ideas you've worked on, the more deals you've closed, the more relationships you've had, the better you get at judging whether or not it's going to be worth it.
At the end of the day the best way to figure out whether or not something is worth doing is to have done many things that weren't really worth doing.
It's just like a muscle you need to exercise.
The more things you did that weren't really worth it, the better you get at spotting the things that are probably not going to be worth it...
[Related: I stopped giving a shit a long time ago]