Just remember not to bash yourself if you do slip up because if you feel like a failure you will punish yourself by smoking full-time again. Instead, tell yourself that you are only human and it's just one and it's just to remind you why you are now a non-smoker. This might sound weird but if you slip, focus on how every drag is making you feel, so that you recognise when you've had enough, enjoy it, no guilt but then stub it out ASAP.