Persistence is key! If you want to expand your knowledge in a certain field, you have to stick with the training/studying on a regular basis. I have not improved my chess game very much over the past decade because I do not devote the time that is required to gain new chess knowledge. I'll study every now and then. I'll study openings, middle-games, endgames and tactics. I forget them, frequently. The problem is a lack of repetition. I am not studying these aspects of the game daily. Chess is all about dedication and training. If you want to remember what you've studied, then you have to repeat it - daily!
This problem has appeared in my life in areas outside of chess - specifically web design, graphic design and studying foreign languages. If I had the will to devoted a significant amount of time to studying these fields I would be a lot better off. I practice graphic design on my computer. I watch Inkscape tutorials on YouTube. I successfully make a logo or twitter header. Then I leave it at that. A few days later everything I learned from that specific tutorial is gone. I need to put in the hours. I need to study both old and new material, daily. Life is not easy. If there is no pain, there is no gain. I need to be more disciplined. I've forgot a lot of French vocabulary that I learned in High School because I didn't continue to study it beyond high school. I need to be motivated. I need to be disciplined. I feel like I've gotten nowhere with life over the passed 10 years. I will make the changes. I will not waste anymore time. Persistence is key!