Here's some good advice I once got if you're trying to give up anything..
Instead of saying something like '"I'm not gonna smoke for a week", try just saying to your self "just one day" or "Just one hour" or "Just one" anything, you know? It helps to break it down aye, if you just keep telling yourself just one more hour with no weed, then when the hours gone say it again.. Its a lot easier then saying your gonna go the whole day without bud.