Sunday is the most predictable day of the week. It starts out with a hot griddle or a waffle iron and a nice family breakfast. Then, a shower and shave before heading off to church. After that comes the LSR: the long, slow run of the week. This is 100% me time.
The distance doesn't matter as much as the time on your feet. I run about 10 miles now, but by the end of the summer it'll be up to 20 or so as I prepare for the marathon. It's a great time to reflect on things, find peace with your inner demons, and gain clarity on what's most important in life.
The run is easy, but it should also be focused. You don't want to run too fast or too far. You need to keep good form and remember to breathe and watch your stride length. The worst thing you can do is turn the long run into something it isn't. Don't get competitive and chase other runners. Don't feel like you need to attack the hills.
Focus on floating. Run. Quietly.