Long hair on men is associated with the cultural revolution beginning in the 1960’s which, among other things, attempted to confuse God given gender distinctions. Though certain individual men in our confused day and time may not have this same intention in wearing their hair long, this practice still makes a counter-cultural statement and not one in keeping with the order found in the Traditional Catholic Faith.
St. Paul spoke harshly against long hair on men in the Scriptures precisely because in his time, long hair was associated with women, as it is in our own. Thus, as a sacrifice to God, and to be more in keeping with Catholic order, the OP should not wear his hair long enough to be seen as participating in any way in the gender revolution and disorientation we are still living in. Besides the gender confusion we also have long hair on men related to the hard rock culture of drugs and promiscuity and anarchy. So there are various reasons men should have a neat and clean cut appearance.