Be flexible on your travel dates

I know this isn't easy.

Travelling requires meticulous planning and finding the best dates and timetables can be a real pain. Especially if you're travelling from overseas and you're looking to squeeze in as many destinations as possible.
Ideally, Crete needs at least 2-3 weeks in order for somebody to really grasp what the island is all about, see a fair amount of places and interact with Cretans who will share incredible stories.
Crete is a vast island, full of diverse landscapes, fascinating historical background everywhere you look. Mountains, lakes, sea, islets, villages, cities, gorge, all blend in one and create a unique mosaic that will definitely charm you. Take the time to take everything in, enjoy the long dinners accompanied by local music and dancing, absorb every little moment with any rush. It is the mellow, laid-back lifestyle of the island that makes it unique. If you feel like you should spend an extra week at a random place you accidentally ended up at, then that is exactly what you should do.

Also, on a more practical note, you might want to be flexible 1-2 days before and ahead of your trip, since unplanned changes can happen. For example, the ferry to/from Gavdos island doesn't travel when the winds pick up, which might leave you stranded on the island for an extra couple of days.