Don't think that you're worth $40/hr, know that you're worth $40/hr. It sounds like you're unsure, and any good business negotiator is going to pick up on that

Don't think that you're worth $40/hr, know that you're worth $40/hr. It sounds like you're unsure, and any good business negotiator is going to pick up on that and use it to their advantage. The way you know is to get paid that much already, or to have multiple firm offers for that much from other potential employers. If neither of those are true, then you don't know what your value is, and you're negotiating from a point of weakness. If you can't reach that level of confidence, then the next best thing is to find out exactly what the job entails, and learn what the local market pays for that skillset. If you bring extra skills, point them out and use them to bring your price up. If you bring only a subset of those skills, use that to set expectations for future rate increases when you can prove you've added value. It sounds like you're guessing as to your worth, and negotiating based on the pay you want. Do the research, get competing offers, and know what you're worth. Be prepared to explain to a potential employer how you arrived at the number. It's the only way to get paid fairly.