Think of how stingy you are with your money: if someone on the street asks for $10, you're not giving it to them. There's no way you're giving a 30% tip for a normal dining experience. And so on.
And yet so many of us just waste ungodly amounts of our time. We throw it away, every day. I know I do unless I'm careful. What helps me to not waste time is to see it as an investment, and to keep track of the returns I get for my investment.
This approach has led me to recognize that some things offer incredible immediate1 return on investment: a night spent learning a new song on my preferred instruments, for example, gives me a lifetime of being able to play that song. That's an incredible return. Other investments are more like low-interest, high security, long-term investments: going to the gym, eating right, etc. Some, like reading good books, are kind of a combination of both.
But many activities are worthless from an investment perspective: whatever benefit they seem to give doesn't last any longer than the activity itself."Price is what you pay. Value is what you get." - Warren Buffett. This applies to everything: money, relationships, time. Knowing this changes your life.