How could reading a form of writing in solitude be considered an individual tradition?
When we analyze what is a tradition we realize that it can be just about any activity that is performed with a specific purpose, and in a systematic way.
Therefore, an individual tradition is a person's own choice of activity conducted during a well-established period of time. In your question you ask how reading could be defined as an individual tradition. The answer to that is that a person can indulge in reading at specific times to become enlightened, entertained, informed, persuaded, or inspired. That is one way to include reading into a schedule of individual traditions.
Reading has always been an very encouraged and rewarded activity among young adults and children because of the many benefits one obtains from it. It helps to keep focus, to concentrate, to soothe, to educate, and to motivate readers to research. The best way to make reading an individual tradition would be to select the correct moment in the day, and the proper place, so that the experience is more fulfilling. Many people choose to do it before going to sleep in order to take advantage of the eye movement done during reading, which helps some people fall asleep. Other people prefer to read first thing in the morning to be able to set time aside for it. In general, reading can be always included in one's personal schedule and it can become an individual tradition quite easily.