I belong to an online critique group, and over the years, I've noticed that some members have a difficult time staying motivated. They're full of enthusiasm when they first join, and then their interest level slips a little, and before you know it, they either participate only occasionally or drop out.
Sometimes it's because the group takes a lot more time than they realized or are willing to give. And some let their commitment to the group slip way down on their list of priorities in life. Others figure they aren't getting published any faster since being in the group, so why bother? There are many reasons, but there's only one solution.
The solution, of course, is attitude. Toss in a little patience and perseverance, and you've got the perfect formula for staying motivated. It's a formula that works for myriad facets of our lives. It lies within each of us to make something work or lose interest in it.