This is an interesting question, because it signals that you are most likely very new to hiring, and maybe ill-equipped to handle managing people in general. Although, at least you're asking questions.
First, very rarely does a manager regret a hire even though it's very common for a hire not to work out. Hiring and interviewing are in terrible shape right now, and more often then not lead to terrible hiring/job acceptance choices.
Second, you regret hiring PEOPLE, not developers because regrettable hires aren't specific to developers. When they are, it's because an engineer was given too much access to something they should not have been and a theft/breach occurs.
Examples of these concepts in play: The NSA probably regrets hiring Edward Snowden. I don't regret hiring the last JS dev I hired even though it didn't work out and he moved to a different company.
Lack of technical expertise is a problem sometimes, but it can be nurtured. Lack of personal skills is a huge problem in an office environment, and is much, much harder to nurture. But neither of these are regrettable in-and-of themselves.
The thing to remember is that you have to weigh the urgency of hiring against the long term impacts of hiring the wrong person. In other words, be careful and set up controls, but don't allow decision paralysis.
Good luck with your project, keep your head up, and expect failure. Great employees are rare, so just keep at it.
post mobile edit:
Go read:
Good To Great: https://www.amazon.com/Good-Great-Some-Companies-Others/dp/0...
How to Win Friends and Influence People: https://www.amazon.com/How-win-friends-influence-people-eboo...
Emotional Intelligence: https://www.amazon.com/dp/B000JMKVCG/