Most authorities recommend some written record, even if it's temporary and on a piece of scrap paper. Learned material is best remembered from the beginning and ends of learning sessions. Long uninterrupted sessions are inefficient. Take a proper break of a few minutes, but be disciplined. Early morning is supposed to be a time when your learning is more efficient.
Early evening is associated with greater efficiency of motor skills and constructive reasoning.
This advice is not usually seen as practical, when one has to live and sleep as well as study. When studying and tiredness occur together, insight is the first thing to go. Learning, for an adult, is melding the new facts in the context of the old in a coherent way. Take a look at this disordered image . The disordered articles make it difficult.