There is no substitute for written goals. To reach your potential you must have them. Read them everyday. Visualize them . Keep a daily log on what you do, how you feel etc.
Every practice missed is an opportunity lost.
Don't make excuses. Take responsibility for your swimming future. Aerobic development must be done at an early age. Your swimming future is limited if you fail to take advantage of distance training at this stage of your career. There will be a time in every great race you ever swim where you have to make a decision - To push on through the pain or to back off.