Spurs host Burnley on Saturday after being beaten at Liverpool last week.
Postecoglou said: "I think I have been consistent in saying we have got a challenge at the moment - a short term challenge.
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"A significant rebuild, and the challenges will always be there and it is how you approach them. Inevitably there will be another one down the road.
"From my perspective, I need to be clear-headed about what we want to do and what we want to achieve.
"It is fair to say everyone is trying hard, it's not because of a lack of trying we need to stay calm and clear-headed."