You will find happy people in all fields of medicine - even those that are extremely stressful and demanding. You will find plenty of people in fields that don't pay much (relative to other fields). The key to happiness is finding something that you enjoy and provides you some sense of fulfillment in the course of the work. Doing that requires that you know yourself well and flesh out your expectations and goals for your life. It's hard to say what field will make you as an individual happy because no one knows you as well as you, and you'll likely start working out what is most interesting when you get into the clerkship year. There are some fields that are relatively "low stress" and "not grueling" as well as "pay well." However, even for those fields the delayed gratification is significant, and you will go through a minimum of 7 years of variable degrees of suck before reaching that point. For some of those fields (e.g., derm), there is no guarantee that you will perform at a level well enough to be a competitive applicant for the field. For others (e.g., psych), the field isn't competitive but is unliked by many people, and there's no guarantee that you wouldn't be one of them.
I suppose the take-home point is that going into medicine strictly with the expectation of "easy job" and "high pay" isn't a good strategy. I would say there are some of those jobs are available (depending on your definition of "easy" and "high pay"), but, as mentioned, there is no guarantee you will have that in your future. IMO going through medical school and residency to land a job in something you hate would be both a waste of time and money. If you don't have some intrinsic interest in what being a physician involves, you will probably be miserable during the journey.