“Pace” means how fast or slow something is. In this sentence, “pace” has a very broad meaning, describing the way people live their lives. You will often hear people talk about “the pace” in different places. Warm, tropical countries, for example, are thought to have a slower pace, while busy modern cities are known for their quick pace. 

You can say “the pace of life,” but if you only say “the pace,” the meaning is the same, and people will understand you. Because “the pace” is shorter, you’ll hear it used quite often.

For me, the pace of city life is energizing.

They live at such a different pace. It’s a real adjustment.