At first I did not understand this concept. Because I had the mindset that whatever I put out I need to be paid for it. When I put the wallpapers up for free I was nervous. More so because I thought nobody will download them.
Then another mind-frame was feeling as if I would not get anything back from it. The same thing for writing blog posts can be a similar comparison. If you are always worried about getting something back then you will be limiting yourself. Because sooner or later you will be paid back for your contribution.
A great example for receiving something back from giving something away for free is when you do pro-bono work. Many people are against it. Well for me it depends upon the circumstances in regards to pro-bono work. Because there are a lot of organizations that will take advantage of designers.
But you have to remember that you have to be willing to work from the bottom up. There are countless amounts of stories of people whom gave their time and dedication away for free and they are people whom you admire nowadays.