I have to focus one day at a time. When I started this 29 days ago I wanted to do the 6 weeks utnil my holiday but I could not say 'I am doing this diet for 6 weeks'. I still can't even say that for a fortnight.
Just take it a day at a time. I keep a diary and give myself goldstars when I've done really well. It might be a little sad to some but for me it keeps me going.