No reason to pull the campaign.
Did you adjust your bids lower? The initial cost per day they quote is based on your ads being in the number one position. Try putting yourself in a lower position... and to be honest, their quote can be pretty far because they are guessing a 5% click thru rate. This could be much higher or lower depending on your ad position and ad text.
Secondly, you can set a budget! Don't want to pay 40 bucks a day? Set your budget to 10 bucks or whatever you can afford at this stage.
If after a week you determine that you make 20$ for every 10$ you spend, then you'll be comfortable raising your budget bit by bit.
When I started I spent 10$ a day. When I saw that I consistantly made more money than I spent, I raised my budget more an more. Today my budget is unlimited, meaning if I can get Quality converting traffic, I will pay for it. I'd love to spend thousands a day.. but their isn't that much quality traffic available to me (at a price that will offer a positive ROI.)
No point in asking other people what their daily budget is... too many variables such as cost per click, ad text, targeting, market, your website, etc, etc.
Set your budget, track ROI carefully, adjust, track some more, adjust, adjust, adjust..... infinity.