It is sometimes said, in the catholic tradition, that morality is not so much about actions but rather about how we view life and what/who a human person is.
It is sometimes belived that we focus too much on sex or other things in order not to deal with who we really are. Some people say that not having any expression of sexuality is bad for us. We are after all sexual beings. We can't just wait until we are eg. 30 years old and married before we start expressing our sexuality.
What does then Church say about how we can, in a morally ok way, express ourselves? Repressing feelings, emotions, sexuality and so on would, I guess, go against what the Church is teaching.
Your question expresses a lot of stereotypes and straw men about Catholic moral teaching, especially in regards to human sexuality. The sad thing is that even some priests actually believe this and they of all people should know better!
Pre-Vatican II, I grant that the Church was too legalistic. This legalism at times became absurd. In celebrating the Old Mass you could commit many Mortal Sins all in the same Mass! The silliness even continued in response to a question about coming late to Mass. How late could you come to Mass before you committed Mortal Sin? If you came before the Gospel was read and stayed through communion you did not commit Mortal Sin. What did some Catholics do? Came late and left early---it wasn't sin so long as you arrived before the Gospel and stayed through communion. Unfortunately this practice continues. Just watch next time you go to Mass. Some people rudely leave right after they receive communion.
Some things Pre-Vatican II, then were silly. The legalism in moral theology in part was due to the Nomianlist influence over moral theologians. Morality was reduced to rules and obligations.
However, if the Church was too legalistic before Vatican II, after Vatican II the Church went in the opposite direction. In reaction to the legalism of the past, priests have not talked very much about sin or what the expectations are of those who call themselves Catholic. They have shied away from preaching about sin, the need for Confession and Grace, etc. They have avoided the controversial church teachings about human sexuality, abortion, marriage, etc. The past 40 years priests and bishops have choose to emphasize teachings we have in common with the secular world like Catholic social teaching. This has lead to a very confused generation of Catholics.
Pope Francis said (not exact quote) "The Church cannot be obsessed with gay marriage, sex, and abortion." While I understand that the pope was well intentioned and his heart was in the right place, I could not help thinking "Is the Church obsessed with those things or is it society that is obsessed with those things?"
This brings me to my first point in response to your question: the Church is not focusing on things like abortion, gay marriage or sex because it is the Church that is obsessed with these things. The Church is focusing on these issues because it is secular society that is obsessed with these things. People are very confused about the nature, purpose and ultimate end of human sexuality and the nature, purpose and ultimate end of marriage. People are very confused about the sanctity of life. It is because this confusion exists and because it is impacting society that the Church has to constantly speak to these issues. I note that what the Church is saying is largely falling on deaf ears, but we must continue to speak to these issues nevertheless. God does not judge us on how many people we converted or how many people listen to the voice of the Church. God judges us on our choice to continue to witness even when our efforts are fruitless or what we say falls on deaf ears. Paradoxically the most important choice we can make is to witnesses in such circumstances. That is when it is the most powerful.
My second point: nowhere does the Church teach that sex is bad, you have to wait until 30 to marry, the expression of love is bad, the expression of feelings is bad, that we must repress emotion, etc. That is a straw man. What the Church does teach is that sex is bad when it is misused. That the expression of love is always good, but there are certain expressions of love that are not appropriate to all relationships. That marriage is good, but it is bad when it is misused. That people should only marry when they are mature enough to understand what it means to be married and mature enough to take on that responsibility and that they should be sufficiently prepared for the sacrament. In short, the Church teaches that all things in moderation and all things within their proper context. Often times the sin in some act is in misusing some gift God has given to us. The gifts of God are intended to be used, but they must be used in the way God intends. When we use the gifts of God in a way God does not intend we sin, even though those things in and of themselves are good.
As for the expression of feelings, emotions, etc, and repressing them, let me be clear: feelings, passions, appetites, etc, are morally neutral. They are neither good or bad, they just are. What we do with them is what matters. One's sexual orientation is morally neutral. One cannot control who or what they find attractive. One can, however, control their actions. We are not animals. We do not act according to impulse or instinct. We act in accord with reason. While a feeling, appetite or passion might be morally neutral, an action is morally good, morally neutral or morally evil. We can't control our emotions, appetites or passions. We can control our actions. We are judged based on our actions precisely because we can control them.
Thus, what the Church does teach is that we are expected to exhibit self control. We are to seek to master our passions, rather than allowing our passions to master us. The Church does not tell people to repress their feelings. Repression can lead to all kinds of psychological problems. People should absolutely own their feelings, acknowledge them, etc. People however need to find appropriate ways of expressing their feelings. People need to exhibit self control when their feelings are leading them to act (act) in ways that are not in accord with right reason. That people are expected to exhibit self control and mastery of their passions does not mean they are repressing or ignoring them. Do not confuse concepts like "repression" with concepts like "self control." They are very different things.
Moral theology is very much about actions. Mortal theology is not only concerned with actions however. Actions both flow from who we are, but they also determine who we are. Actions both constitute us and determine us. This is why it is our choices that determine who we are and it is our choices on which God will judge us. Moral Theology is also about who a person is. Mortal Theology is about both who a person is and actions. Do not create a dichotomy between them as if they are mutually exclusive. They are two sides of the same coin. An over emphasis on actions will lend itself towards legalism. An overemphasis on the human person can lend itself towards subjectivity and thus moral relativism. Both must be held in a healthy tension.