We always make important decisions in a thoughtful manner.

thoughtful 是由名词 thought（思考）加上后缀 -ful（充满...的）构成的形容词，意思是"经过充分考虑的、深思熟虑的"。后缀 -ful 表示"充满某种特性"，所以 thoughtful 字面意思是"充满思考的"。