There will be hard times at three weeks, three months, six months, and other times in between.
When I quit I just assumed it was not going to be easy. People told me that and I believed those who went before me.
Thoughts are just thoughts, they can't pull out your wallet - so why get upset about them? I get thoughts I don't want all the time - "How will I pay for this or that bill?" "Why did such and such happen?" "Boy my friend's husband is hot," lots of weirdness flows through my head.
Just find a way to let the thought go...there are lots of techniques - Google "thought stopping" or "urge surfing " or "letting go."