Here is a list of chess tasks that should be performed each day if you seek to improve:
1) Review Master Games within your Opening Repertoire
2) Specialization Position Training out of Opening Repertoire
3) Tactics Drills
4) Endgame Studies - R+P(s) vs R+P(s); R+N/B vs. R+N/B; K+P vs. K+P
5) Daily Play - G5, G10, G15. Weekly - At least 1 Standard Time Control Game
6) Review Your Losses!
This list covers all aspects of play: Openings, The Middlegame, Endings, Strategy, Tactics, Play and Review of Games.
#1 will help you develop a sense of the strategical themes in your choice of openings, and what types of positions to expect from those openings. #2, critical positions taken from #1, will help you understand the strategic elements of the opening/middlegame and the transitions into the endgame. #3 will keep your tactical eye fresh - it can get stale. #4 will naturally improve your ability to finish your opponent off and not fear transitioning into a won endgame from an advantageous middlegame. #5 will allow you to test your knowledge and gain feedback from your play. #6 You cannot improve if you do not know your weaknesses!