Salt is unique in that it is bitter on its own, yet sweetens and brings out the taste of that which it is added to. For this reason, salt is the staple of suffering.

There are two perspectives of suffering – Purposeless Suffering and Purposeful Suffering.

Purposeless Suffering is suffering without reason, value, or an end-goal, and is therefore completely bitter. It is based on a keyhole view of life: “What is right in front of my eyes is all there is and there is no grander scheme.”

We squint in order to focus on something in the distance.

The Kabbalists explain that for this reason, the reaction of a person in pain is to close his eyes, since physical eyes don't see the spiritual purpose. Just as a person squints, which is a partial closing of one's eyes in order to focus on something in the physical distance, one may close his eyes completely in order to focus on something in the "spiritual distance.”

Purposeful Suffering is sweetened by understanding the greater context – that all is from God and for the best.

At the Seder, we dip the Karpas into saltwater in order to embody the concept of Purposeful Suffering – that we view any suffering in life as a surgery for our ultimate betterment rather than meaningless torture. (Additionally, we dip Karpas into salt water to represent the tears cried by the Jewish people while enslaved under Egyptian rule.)

We see these two sides of salt expressed by the Dead Sea. Due to its high salt concentration, the Dead Sea contains no life within it, yet has an incredible capacity to heal. On its own, the Dead Sea is "bitter," but when a person dips into the Dead Sea, he is "sweetened."

בָּרוּךְ אַתָּה יְיָ, אֱלֹהֵינוּ מֶלֶךְ הָעוֹלָם, בּוֹרֵא פְּרִי הָאֲדָמָה

Baruch Atah Adonai, Eloheinu Melech ha-olam, borei p’ree ha-adama.

We praise God, Ruler of Everything, who creates the fruits of the earth.

We also dip Karpas to help us remember the sweetness of life. How the universe  works in cycles and the spring will always come back around providing us with new life.