Signs that you are simply kidding yourself.
In my experience, no entrepreneur is fully prepared for the journey they are embarking upon when they start a new business endeavor. You simply can't have everything you need before you begin this journey. Being an entrepreneur is about being resourceful, or as Paul Graham puts it, being "relentlessly resourceful". You'll need to solve problems as you go and you can't anticipate every hurdle you're going to have to overcome. Ask people around you if they would describe you as resourceful. Ask yourself this question. It is the one skill that every entrepreneur needs to have.
That said, I think you can try to stack the deck in your favor before you begin. Money, knowledge, a head start on your product or service idea before you go full time, the right partners, and the support of your significant other are all things that will greatly benefit you.
In the end, you're going to have to be willing to do whatever it takes to make your business endeavor a success. You're also going to have to be willing to work hard and live an unorthodox lifestyle while you are getting things started. If you're not looking for this kind of life and you don't want to give up a lifestyle that you've become accustomed to or if you don't have the confidence that you'll be able to figure it out as you go, then you may not be ready yet.
I've always thought that you never really know what you are capable of until you are put in a position where there is only one way forward and failure is not an option. In this respect, sometimes I think it's worth a try if starting a new business endeavor is something you've thought about for a long time. Don't be afraid to put yourself out there to see what you can do.
I know my experience of starting a business was one in which I didn't have many things going for me, but I still managed to find a way to make it work and find success.
Work hard. Don't give up. Strive to be the best. Do whatever it takes. You can do it!
any entrepreneur who is worth his salt has a list of past situations he/she wishes she could redo. As hard as you try you are not going to get everything right the first (or even second!) time around. The key take away here is to be focused but not spend too much time second guessing your self. If you go down this path you will get nothing done and you will make your self crazy. The second is to pick a strategy and commit to it. Once you are already going down a path you have to own it. Executing strategy is a 'wishy-washy" fashion will surely yield failure. Other than that you need to be the kind of person who does not blame others for failure. Once you begin your business endeavor you have to be comfortable knowing that everything that goes wrong is your fault. The buck stops with you and is your responsibility to repair the product/service and the customer relationship. So, as long as you are willing to own those processes you will be just fine. You can get advice on the accounting and legal to smooth your path with the logistics, but you have to have the heart for this kind of journey and nobody can answer that except for you.
A key sign would be if you were doubting yourself before you start. To be unsure if it will succeed is one thing, to be unsure if you should even start, disaster.