Tapa loka introduces austerity as a deliberate limit in service of something that matters. The arrow from 28, Sudharma, ends here, linking a chosen path with the effort of practicing it.
A limit might mean protecting time for study, spending less on something you do not value, or keeping a manageable daily commitment. Its usefulness depends on what it supports. Discomfort by itself is not evidence that a practice is worthwhile.
Consider a discipline you have chosen or are considering. Can you explain its purpose in plain terms? Does it leave room for changing circumstances and ordinary needs? A practice can be serious while remaining proportionate.