It's the fear of the end result that causes you to panic. Just calculate all the numbers, and it's okay if you realize you're spending too much. That's how we budget. After we see it all on paper, we can then figure out where we can spend less so we can save more. Pretend you're a financial advisor if you have to, and you're looking at someone else's expenses.
Just remember, they're only numbers. And numbers can easily change. You'll do just fine! :)
"Never give up on something that you can't go a day without thinking about."