Yom Kippur is all about love and forgiveness. It's about how we are always inseparably close to G-d. On Yom Kippur we get a glimpse of ourselves, our choices and our relationship to G-d from another perspective--G-d's perspective. This is the transformational power of Yom Kippur that makes it into a Day of Atonement and forgiveness.
There is a cryptic verse in the Book of Psalms (139:16), which, the Sages say, refers to Yom Kippur:
The days were formed, and one of them is His.
Every day of the year we see the world from our perspective, but there is one day--G-d's day--when we get a glimpse of the way the world looks from His perspective, and everything changes in light of that perspective. On Yom Kippur we see it all from the perspective of the World to Come where you get to see the whole picture.
The Talmud teaches that in this world when something good happens to us, we praise G-d--"Blessed is He who is good and does good." When something bad happens we must say--"Blessed is He who is a true Judge." However, in the future we will say, "Blessed is He who is good and does good," even about the misfortunes in our lives.
In other words, when we will look back and see the whole picture, we will realize that every bad act we chose and every dark event that happened to us, contributed to G-d's plan--to bring upon us ultimate goodness.
On one hand, we have the free choice to do other than G-d's will, and yet G-d is always in control. Therefore, although we can do other than G-d's will we cannot oppose His will or undermine His plan.
Therefore, when we have done wrong and are sorry for that, we must realize that no matter what we have done it can all be recycled back into G-d's plan and contribute to the ultimate good.
Of course this does not mean that we can just go ahead and do wrong. The path of transgression removes us from G-d. This distance causes us feelings of alienation and spiritual anguish which may even become manifest as physical ailment.
However it is important to remember that if you sincerely regret your negative acts, resolve never to do them again and fix whatever damage you are able to fix, then you are forgiven and your past will be recycled and put toward future good.
Yom Kippur is an amazing day of transformation where your darkest deeds from the past turn into light. This is because the light of the World to Come, so to speak, is shining into our world on this day. You can receive this light and be transformed by it if you plug yourself into the expanded consciousness of Yom Kippur through the proper acts, prayers and thoughts prescribed for the day.