Medical school and residency training usually decrease one's happiness for several reasons. Happiness researchers have demonstrated that a feeling of control and the amount of spare time one has both correlate with happiness. Both of those factors are limited during med school and residency. Relationships are also correlated with happiness, and those can be squashed during medical training as well.
I'm not trying to be a downer here! I want to encourage applicants to consider this happiness quotient when selecting an institution and training program. If you are able, maximizing your contentment by choosing an institution that fosters your greatest happiness is key. Geography; proximity to family, friends and community; and a location that provides an opportunity to enjoy hobbies during limited free time is significant.
Excellent training is important, but, in the end, many programs turn out equally qualified clinicians. At least consider your well-being as a factor in selecting where you might be for the next three plus years of your life.