1) Trying to fix that old computer is a waste of effort.

2) Arguing with the stubborn customer proved to be a waste of effort.

3) Spending hours organizing the files ended up being a waste of effort.

4) Pursuing a career in a field you have no interest in is a waste of effort.

5) Trying to teach a dog to meow is a waste of effort.

6) Negotiating with someone who refuses to compromise is a waste of effort.

7) Cleaning the house before a party only to have guests make a mess is a waste of effort.

8) Trying to convince a closed-minded individual to see your perspective is a waste of effort.

9) Investing time in a relationship that is clearly one-sided is a waste of effort.

10) Working on a project without proper direction is a waste of effort.