Ok this is my own running tip from my own personal limited experience and novice physical fitness knowledge. If you lend any credability to me, you're gambling. <G>
I found at the start that I was struggling. I'd look at my fitbit ( its a watch too ) and check the time constantly. OMG OMG OMG just 2 more minutes and I can walk again. My body knew it was about to get a rest and it fought me hard to convince me it was out of gas. It's not!! Your body will sabotage you every single time it can. You're brain is lazy. You must fool it!!! Stop looking at the time. Run until you're told to walk. Your body doesn't know when it's going to rest and can't poop you out in advance. Just a nice comfortable pace and get lost in the music. It really really works for me. I think you should try it and tell me your fidnings. Keep your body guessing.