The best blogs I have ever read are usually about one simple incident in someone's every day life that brought meaning to them. You might often get writer's block and don't know what to write about but you would be surprised that if you just write about your day or a memory you had that sticks with you, you will find deeper meaning you can share with the audience.
Keep it Simple
What did you see today? Did you go outside, if so, what did you do? Why did you do it? People are often interested in the mundane things in life and even enjoy reading about what you ate for breakfast!
Sometimes the purpose of the content will come to you AFTER you start writing, so don't worry so much about writer's block and "free write" whatever comes to your mind. You can always edit after you start so even if it doesn't make sense at first eventually something will seem significant to you.
Nice! I got some idea, I'll try it next time.. I really don't know what to write next.