The real reason for this gap is rather simple: Liberals are always chasing “Utopia”. The are obsessed with these basic ideas:
1. They are the future
2. The are building a Utopian future
3. Only THEY know how to do that and, therefore, they are BETTER people and EVERYONE needs to listen to THEM
It should be obvious that those tenets are NOT a formula for happiness. Indeed, just the opposite. Especially because their Utopia often turn out to be dystopias. Not just for everyone else, but for them as well. But they will never admit that because it would be tantamount to admitting they were wrong about a lot of things. As a result, they become bitter, neurotic and angry.
In contrast, Conservatives tend to assume that just by working hard, being a good citizen and taking care of their families, the world will naturally become a better place over time. While they often try to institute better, more common sense, policies, you don’t often catch them preaching some Utopian ideal.
Even more basic...
Conservatives accept reality as it is and work to make the best of it.
Liberals can’t stand reality as it is and are constantly trying to “fix” it, thus being eternally frustrated... and thus unhappy.
What would help them is the Serenity Prayer.