As has been pointed out by the other posters, the rule is that you can receive twice a day in the right circumstances, more than that if you are in danger of death (or, for example, if you’re a priest celebrating multiple masses in the same day or something).
This rule is purely a practical one. The Eucharist has been called the source and summit of our life and worship. We Catholics rightly have a huge devotion to, respect for, and love and worship of, Our Lord in the Eucharist (in which we believe He is really present).
There are people who, if they were allowed to receive more often, would literally spend their whole day attending Mass after Mass in order to do so, to the neglect of everything else they need to do in their lives.