Running successfully requires speed, strength, and the proper application of rest/recovery. If you were to run hard everyday eventually you will not make any progress. Those athletes that make the incredible mistake to run hard every day plateau quickly or get injured and they find themselves tired and frustrated.
With good programming that applies the principles of speed, strength, and recovery it is possible to achieve your goals as long as you are mentally able to compete well.
Another key aspect to successful programming is understanding the principles of adaptation and specification. Adaptation basically means that your body will adapt to higher stresses placed upon it (like keeping a faster pace) over time. If you don’t continue to stress it after a while you loose the adaptation or if you don’t give yourself enough time to adapt you can overtrain so it is a delicate art to know how to manage adaptation.
Specification means that you will adapt to specifically what you train. If you train for a specific pace over a specific distance then you will adapt to that specificity.