“I count my blessings every single day.”
You took a great photo of your family, and now you're sharing the photo on social media. You write something to show how happy you are about your wonderful wife and children.
I count my blessings every single day.
To "count your blessings" means to feel happy about the good things that you have in your life: your family, your good health, your wealth, and so on.
Use the phrase like this:
You have so many reasons to count your blessings.
People who are religious use this phrase more than people who aren't. That's because "blessings" means gifts given from God.
"Every single ___" has the same meaning as "every ___":
I meditate every day.
I meditate every single day.
Adding "single" simply emphasizes that you really do mean "every":
A: Did everyone die?
B: Yes, every single person.