The training is the hard part...
Recently another redditor posted this excellent thread:
https://www.reddit.com/r/beginnerrunning/comments/1tan7my/longer_is_not_always_the_next_step/
while I agree wholeheartedly, I did think there was another critical point that I wish beginners understood.
That point is simply this:
Regardless of the distance you are training for, the TRAINING is the hard part. The race is simply the victory lap.
We had a lot of folks arguing in that thread about what race distance is hardest or how a particular time in one distance compares to another distance. While we can look at charts online and say for example that a sub 20 5k compares roughly to a 3:10 marathon, that comparison is meaningless if you don't train for that event.
Keep in mind that regardless of the distance of the race, it's your training that largely determines the outcome. If you focus on the training rather than the race, you'll up your chances of success tremendously.
This is why I personally get frustrated with the posts here from people that ask how to reach a particular goal such as completing a race or running a particular time, but then ask how to do that without doing the requisite training.
Simply put, the training IS the thing. It may not look as sexy on social media, but it's what really matters.
All the best.