I know many bloggers do this. You don’t necessarily need to have a notebook like I do, but you do need to have somewhere where you take note of your ideas as they emerge. There’re lots of mobile phone apps and PC software like evernote that can help in this respect.
You're a writer. You write, but when it comes to blogging, you freeze.
I know you do, because you tell me. :-)
Blogging is more a habit than anything else. After 12 years of blogging, it's a well-engrained habit for me, and it's helped my writing (hand on heart) more than anything else.
Yes, blogging can drive you demented. Your blog is always hungry, BUT you've got other writing to do as well -- paid writing.
How do you come up with ideas for blogging when you're tired of writing?
You plan for it. The above article gives you some ways to find inspiration for blogging.