1. You start too fast and try to run too far too soon
You head out the door and run for as long as you can with no control over your pace. This is so painful you won’t get very far or if you do get far (as I did, that one night in London because I had no other choice) you won’t want to do it again unless you’re some sort of a torture-loving superhero. To make it easier, start with short running intervals mixed with longer walking intervals. Stop before it gets hard. Give yourself plenty of time to be a beginner, the slower your progress, the better your chances of keeping it up long-term. Learn to control your pace, you need to run slowly, not sprint, so you can keep it up longer.
2. You don’t know how to control your breathing
Running is all about aerobic fitness which is all about breathing. Oxygen is fuel for your muscles so if your breathing isn’t efficient, you’re going to wear out. One common breathing mistake people make, for example, is when they get out of breath they try to breathe in more without properly exhaling. Unless you empty your lungs fully, there is no space for more air in your lungs so your focus should always be on the exhale, which should be long and steady, rather than on the inhale, which happens naturally.
3 You’re too focused on your end goal
If the only reason you go out for a run tonight, is so that you can run a 5k at some point, you’re unlikely to get to that goal because it’s so far away and takes a lot of work OR if you do get there, it’ll be a painful and boring process. It’s ok to have that goal but it should not be your main focus. The most important thing is to learn to enjoy running so much that you go out for a run just because it’s enjoyable today. This is living in the moment, enjoying life and with this approach, you will be able to keep it up long term and you’ll reach that 5k goal easily with a smile on your face.