Karma

"...But in Buddhist science, karma has nothing to do with fate - it is an impersonal, natural process of cause and effect. Our karma at a given moment of life or death or the between is the overall pattern of causal impulses resulting from former actions connected with our life-continuum. These form a complex that impresses its effects on our bodies, actions, and thoughts. In turn, our ongoing actions of body, speech and mind form new causal impulses, which determine the nature and quality of our lives in the future. This complex can be called our evolutionary momentum.

There is an old Tibetan saying, "Don't wonder about your former lives; just look carefully at your present body! Don't wonder about your future lives; just look at your mind in the present!" This expresses the sense that our present body has evolved from a long evolution driven by former actions, and our future embodiments will be shaped by how we think and what we decide to do in our present actions."

Page 28. The Tibetan Book of the Dead [The Bardo Thodol]
Translated & Introduced by Robert A.F. Thurman