I've had blogs on and off for years (since back when they were called "online journals"
) and my most constructive advice to you to get over the nerves is to just write for yourself. Don't think about writing well or what you're sharing or catering to an audience. Just write, and write from your heart.
For me, writing is one of the most cathartic things in the world. It's a way to get it all out, it's something to look back on and see how far you've come or where you still need to go. It's my brain dump and my sanity.
Just relax and start typing. You'll be amazed at all the awesome things that come from that simple beginning.