This is my own secular perspective and I have very little religious training and knowledge. However, I appreciate tradition and its importance in binding together for 2000 years the Jews dispersed all over the world. Preserving a common identity without sharing a geographical territory (before globalization and virtual communities) while making many important contributions to humanity in different fields of science and arts, and building a modern state on the biblical lands (i.e. sand) after loosing 6 million souls during WWII is no small achievement. Tradition shapes our identity, help us belong.
Some holidays remind us of important events in Jewish history (a subset, such as Hanukkah and Purim, falling into the 1-2-3 category, where 1 = They tried to kill us, 2= We survived, 3=Let's eat) and some are connected to agriculturally meaningful times and even taxes. Although tempted to categorize the holidays accordingly, I am leaving this task to knowledgable scholars. What I want to discuss is the theme of taking things for granted, which so much caracterizes our modern lives.
The things we take for granted are usually the needs situated on the lower levels of Maslow's hierarchy of needs pyramid.
Passover teaches us not to take food for granted, by forbidding bread, the most basic food, for an entire week. But most importantly it teaches us that freedom is worth believeing in. I would parallel that to Maslow's self-esteem layer.
Giving up the security of our home during Sukkot to live in a booth teaches us not to take shelter for granted. The hospitality tradition touches on higher social needs. We can expand the notion of physical security to all sorts of other securities, including the financial one.
Before Yom Kippur, Jews seek forgiveness for wrongs done against God and against fellow men. If your 'fellow men' don't forgive you, neither will God, fast or no fast. This is about mantainance of relashionships, the 'Love and Belongingness' layer of Maslow. Do not take the love and friendship of those who surround you for granted.
According to the arameic saying in the Talmud, "me'igra rama ad bira amikta", falling from the greatest heights until the lowest depths can happen pretty fast. Extreme changes can happen suddenly. So is there anything we can or should take for granted? The only thing that comes to my mind is that the sun will continue heating the Earth for the next few million years. If an astroid won't change our orbit.