Every race is totally different.
I often lose motivation, but it's something I accept as normal.
Age 50 is a lot tougher than 40s
The advice I have for beginners is the same philosophy that I have for runners of all levels of experience and ability -- consistency, a sane approach, moderation and making your running an enjoyable, rather than dreaded, part of your life.
A change of pace in terms of your running pace will give you strength psychologically.
Hills are terrific for running