Stop looking for the perfect workout. Simplicity and consistency beat complexity and novelty every time. Run often, mostly easy, sometimes long, occasionally kinda hard, every so often very hard. Take care of your body. Do all this for years on end. If there's a magic formula, that's it right there.

General rules of thumb to keep in mind for both running and life: Good things take time, complexity often leads to complications, and the “boring” way is more often than not the best way.