Anice course goes a long way (ha-ha) toward making a long run enjoyable. If you can, include other elements so that long-run days are ones you really look forward to. Run them with friends. Go out for brunch afterward. Schedule a massage. Have a soak in a hot tub or bath. Do them on unharried days so that you can relax afterward and enjoy that pleasantly fatigued mellow feeling.
Most days you’re going to scramble to fit your running around the rest of your life. Try to have long runs be one of the centerpieces of your day once in a while. You’ll be reminded of the many things you love about running.