This has been the biggest game changer for me. People often think they need to push it hard and they quickly fatigue, burn out and hate going running. The trick is to do a 80% of your running sessions in zone 2 and 20% in high intensity to increase VO2 max. If you are at the start that means sometimes walking on hills and that is ok. There is a great book about this: https://www.amazon.com/80-20-Running-Stronger-Training/dp/04...