When running farther, your mental preparation isn’t actually the only factor to doing it. If you want to run as farther as you can, you need to prepare your body as well. While you don’t really need to do an extensive warm-up and stretching session like if you were to run at your maximum speed, you only need to do a few exercises to prepare your muscles for more strain and to prevent yourself from getting injured (don’t forget to cool down as well after every running session).
I know that most people are impatient because they need instant results. However, if you want to build up a good running endurance, then patience must be in your gear bag. Good runners usually put in very small increments that most people don’t notice. However, after several weeks or even months, these small increments become very obvious to anyone. Try increasing your distance by 5 or 10% each week. When you first start, try to measure what’s your maximum distance that you can’t cross. You should stay in that zone until you become comfortable with it. After a week, try to increase it a little and get comfortable to it and so on and so forth.
I always perform better when I have company with me. The reason behind this is that you get motivated when someone is running with you. Motivation is what keeps a beginner runner away from giving up on running the first few weeks. So try to make use of it.