The first step in becoming a better cyclist in any discipline is to do the right kind of training at the right time. Worn-out clichés like “no pain no gain” are relics best forgotten (at least insofar as they imply that all riding should be hard).
Before we start with incorporating structure, it’s important to know where you are and the various systems needing attention. For that, here is one of my favorite articles by Andrew Coggan, one of the world’s foremost authorities on training: Power Training Zones for Cycling