I have done some bad things in my life, and find it difficult to change. How Buddhism can help me get past that?

There are people who may have done something very bad in their life, and because of the guilt, they live under the impression that they cannot recover from that, they will always be like that, there is no changing.

The practice and understanding of impermanence allows us to understand that we do not have to continue to allow these bad things to happen. We can start a new life, we can have a new light in our life. 

We do not need to be influenced and go on with the same storyline. We can start a new story. When we meditate properly on impermanence, we see that every moment there is an opportunity to start again. It is always possible to begin in a new, positive way.

HH, 17^th Karmapa
Ogyen Trinley Dorje

From Kamashila
Short-Ngon-dro teaching
Germany, 2014