It is quite a rollercoaster. Especially if you have been in a place for a long time. In my case, for example, it was ten years with the same company. There is no doubt in my mind that after such a long time I have developed the "Shawshank Redemption" syndrome. All kinds of thoughts come to mind. Fillings of fear, doubt and anxiety. All part of a journey. I have quit my job 3 months ago to explore self-employment.
I am not gonna sugar coat. The first few weeks were hectic as hell. So many things to organize so many things that I didn't have to deal with before. It is very easy to get overwhelmed. What you have to keep in mind is that eventually, the dust will settle. Take it a day at the time, a step at the time and before you know it all these new things will start to look familiar, almost effortless.
Still, I would say learning new skills and adapting new behavioral habits is the least of your worries. The mind games that will be played in your current workplace are probably the most difficult to deal with. Most people will not look kindly on you trying to move to do better for yourself.
Especially, if they have relied on you heavily. I don't think it has anything to do with jealousy. It simply means that they would have to adapt to this new situation as well and change doesn't come easy. On the bright side, you will learn who your real friends are. Those will be the people who will keep in touch long after you left.
As a final thought and perhaps a bit of advice I would say this. If you are thinking about it several times a day nearly every day it means it is time.
Otherwise, your mind wouldn't be preoccupied with these kinds of thoughts. Build a bit of financial buffer. Save if you can, an equivalent of there to four months worth of your bills on go for it.
Perhaps Warren Buffet said it best: I think you are out of your mind if you keep taking jobs that you don't like because you think it will look good on your resume. Isn't that a little like saving up sex for your old age?
thanks for comment, love the quote :)