The tourists lost by five runs in Adelaide as they suffered a 4-1 series defeat at the hands of their bitter rivals.
However, Cook believes that England got themselves into a situation where they should have come out on top as they tried in vain to chase down a modest target of 218.
"We should have got over the line," BBC Sport quotes Cook as saying.
"We got into some good positions. Credit to Australia as they held their nerve better than we did but there were some poor shots.
"It's been a tough couple of months. We've got a lot of things we can work on. There's a lot of talent and in 12 months' time we should be in better shape for the World Cup."
England's limited-overs side returns to action next month when they travel to the West Indies for a short tour ahead of the Twenty20 World Cup.