What are some ways to not waste time thinking about what others think of our actions?
Do you know about the Spotlight Effect ?It is a psychological phenomena due to which humans tend to feel that they are being noticed more than they actually are. Basic analogy behind this is that though we are centre of our own universe, we are not the centre of everyone else's. This term has been coined by Thomas Gilovich and Kenneth Savitsky. So the next time you do something embarrassing, don't sweat it, because there is high probability that no one noticed, and even if they did, they don't have the time to care.
Why has caring about others become a bad thing?
Because the simplest way to discredit someone is to throw a big label on them, find one area under that label that you can attack, and impute the attack to everything else. It's mindless and it's meaningless, and yet it has become the national pastime.
Do you care what others think about you?
I really don't. I used to, but now it's like if someone talks about me I'll just be like "whatever" and go on with my day. Or I'll just insult them beyond what they can comprehend and then I'll go on with my day. :]
What is not a waste of time?
a) things that make you and/or other happy b) things that help you and/or others that basically sums it up. For instance, studying might not make you happy, but it helps you, and therefore it isn't a waste of time. Yahoo answers isn't a waste of time unless the questions are pointless. Now that I finally finished this answer, I realised it falls into the 'waste of time' category.