Happy are the hungry - Blessed are they which do hunger & thirst after righteousness

There are many things for which we hunger and thirst. Or we may say simply, many things for which we desire, or long for.
The words hunger and thirst speak of a craving. One who is famished and is yearning to be filled. We spend a great deal of our lives seeking to satisfy different desires that we have. Such as love, attention, success, wealth. Or even those things that the body craves such as food & drink. And there is nothing wrong with a reasonable or governed pursuit of these things, however the Lord here does not tell us that these things will either satisfy/fulfill us, or bring happiness. But rather blessed (happy, fulfilled) are those that hunger after righteousness.