An idea, a person, a technique, or anything that's very important for making something successful is called "the key":

My key to success has always been getting out there and practicing harder than anyone else.

Dalton's hard work was really the key to the success of the entire event.

Publishing so much content is a constant struggle. The key is not to spend too much time on any one part of it.

There are some other phrases that use the word "key" in this way:

The key factor in my decision was the cost. The Panasonic was a hundred dollars cheaper.

Senator Donnely was a key player in getting the bill passed.