We don't want to be injured! There is nothing worse than an injured runner! Why is it important that you stay injury free?
Endurance is built over time. It takes months, not weeks. You can't just download an app and be ready to go! This endurance is built by weeks of consistent training. You can't get that if you injured. You'll be starting and stopping, unable to build any momentum or rhythm in your training, and will see minimal improvement.
Sometimes you'll have to make hard choices in order to stay injury free, saying 'NO' to a run, taking some time off during the year to just not run for 1 - 2 weeks and let your body and mind recover. This will help you in the long term, but at the moment in can be tough.
So often we see runners push on through a niggle, believing in miracles, and if they just get out and run it'll get better. It doesn't. You then end up doing a half hearted session or run for the sake of it, and when your body finally breaks down you need to take weeks, months or even a year off!
Be patient with your body, it takes time to adapt. Most importantly, stay injury free and you'll see massive improvements in your running over time.