Yom Kippur/Day of Atonement
LEV.16.29
Leviticus 16:29-34
This is considered the highest of holy days. It is almost always connected with some kind of fasting. There is no work to be done. Typically, it is a time of heavy reflection and deep prayer. It is a time to look back and ask forgiveness for overlooked sins and transgressions. Broken relationships should be addressed if possible, and asking/granting forgiveness is something that should be done.
It is a special set apart day to dedicate to getting right with others and with Yahweh. Fasting is biblically good for our body and soul. It allows us to connect more closely with Yah.
Our personal tradition includes writing a personal letter to Yahweh throughout the day. Listing our failings, pains, and shortcomings. We ask him for forgiveness and repent from continuing to those things. At the end of the day, we offer the letters up as a burnt offering. This has a spiritually releasing effect. We believe it truly honors Him.
This website has good basic information on the holy day:
https://www.ifcj.org/learn/jewish-holidays/what-is-yom-kippur