A caveat to my previous comments about exercise always ’ making" me feel better is that what is essential I have experienced is the correct judgement of training at any point in time regarding how you feel. I find teaching people how to judge ’ what type of work to do when ’ is difficult unless that person is vested in their training methodology. Most people want recipe training. Having said that you can’t have every athlete questioning all things all the time with coaches either but it’s a balance depending on the situation.
You see TB you are young and have lots of time and you are making a time and energy commitment into taking a very active role in your training through research and reading and questioning. This is an excellent way to learn more about yourself and what you might be capable of accomplishing.
Generally speaking I will tell you that most people over train, do not understand the various attributes of certain types of training ( high intensity, low intensity, the effect of too much volume ). As a general rule if you error on the side of less you will do better long term. Now, high performance is a different beast all together. At the highest level the game and stakes are raised to meet the possible rewards ( or perceived rewards ) of the outcome.
I am not so surprised to hear that your speed may be decent despite not focusing on it the way you felt you needed… Understand if you were a pure sprinter that pattern would not be sustainable. Retaining speed at a certain level for a period of time is one thing but the greater your goals and the higher you go in competition the more speed work will need to be developed, maintained and routinely practiced. I think you understand this anyway but I wanted to make the point regardless.