A Jew learns from the Passover meal the story of the exodus from Egypt and the commentaries of scholars through the ages on the significance of the exodus story. Everyone has a book called a Haggadah, which contains all of this, and which allows everyone at the meal to follow along and/or participate as the story and commentaries unfold.
There are many symbolic foods during the meal, meant to represent important elements of the exodus. For example, there is matzoh, which is unleavened bread, symbolic of the haste with which the Jews had to leave Egypt, with not enough time to allow their bread to rise. There is charoses, which is a mixture of wine, nuts, cinnamon, and apples, representing the mortar that the Jews had to make when they were slaves in Egypt. There are bitter herbs, usually horseradish, to help Jews recall the bitterness of slavery. Each symbol is explained at the meal.
How a Jewish person might feel if not able to celebrate Passover would probably depend on the circumstances which prevented him or her from celebrating. There are situations in which it could be difficult to do so, far away from one's home, with not all of the foods available, or a group to share the meal with. I think it would be more a question of sadness than of guilt, although Jewish people are called upon to celebrate the meal, so they can never forget.
A person who cannot celebrate the traditional way might gather together some people to do the best he or she could. Haggadahs can be ordered on-line, and most places, at least some of the food should be available. The important thing is that the story be told.