To demonstrate: Imagine someone who realizes that altruism is wrong. He understands what a sacrifice is, and why it is a bad way to live his life. However, subconsciously he still holds years of automatized appeasement of people he loves and avoid hurting their feelings.
When he faces a conflict about appeasing them or acting selfishly, he experiences conflicting emotions. On one hand, he wants to do what's right. On the other hand, he feels the pressure of guilt to act like he has acted in the past - not to be bad, not to hurt their feelings.If left unsolved, he is bound to either act against his emotions and feel guilt, or act according to his emotions and again feel guilt for not doing what he consciously know is right.
Psychological heath requires that a man acts to satisfy his emotions and give them physical form in his every day life. This could be having sex in response to sexual desire, avoiding a painful situation, refraining from actions that makes one feel guilty, eating a candy one desires, etc'.
However, pursuing emotions blindly can be bad for one's long-term happiness. To illustrate: In all these examples the emotion (sexual desire, pain, guilt or "spiritual" hunger) could be a response to wrong premises with results such as being attracted to sluts, finding introspection painful, feeling guilty for telling someone a painful truth because it hurts their feelings, or wanting to stuff one's face with food to dull chronic anxiety.
And just as a diet alone will not work for the person from my last example - so will change of behavior with accordance to an understood system of ethics by itself will not work to make a man happy. It is insufficient.
Ethics and psychology are bound together. Ethics is a science that teaches a man how to live and achieve happiness. Psychology teaches him (or should teach him) how to integrate what he knows by reason - with his subconscious. To correct wrong subconscious ideas and methods, and as a result to be able to experience the correct emotions in response to his environment and to himself.
To summarize and repeat: To achieve happiness, a man must work to straighten his subconscious ideas to match that which he consciously holds as true.
Concretizing what you learn and making your understanding of ethics very very good helps a lot (and in fact does most of the work) of reprogramming your subconscious. However, introspecting the content of your subconscious and correcting it is a necessary supplement (for achieving happiness).
We humans are built to use emotions as motivation force. Emotions not only tell us if something is "for" or "against" us, they also suggest and "push toward" a certain course of action (like running away from danger, acquiring the subject of one's desire or avoiding pain). Emotions (every emotional reaction) lay on the sum of one's subconscious knowledge - which is huge. And at the same time the emotion we feel arises quickly in response to a given situation. This makes emotion highly valuable tools of survival since they provide a "driving force" toward a certain course of action quickly, while taking under account vast amount of information (all your knowledge, essentially, that you acquired since you were a baby).
Therefore, psychological health requires that a man be open in his life to act to satisfy his emotions, to be motivated and guided by them (with reason as the final arbiter). To be closed to your emotions and treat their satisfaction as secondary or meaningless is to pursue something other than your own happiness, and to detach your values from that which you desire - making the pursuit of your values a purely intellectual matter, without enjoyment.
To give content to your emotions (dictate the content of your subconscious ideas) and make them reality-based, and non-contradictory - a man must use reason. Emotions should be the primary driver in your everyday life with reason at their constant check-up, and long-term maintenance worker.