Not every painful experience is virtuous, and deliberately seeking harm is not the goal. الْمَكَارِهِ points to the discomfort often involved in worthwhile obedience: maintaining prayer, telling an inconvenient truth, fulfilling a duty, or resisting a prohibited temptation.
For example, sustained study can be tiring but worthwhile. Similarly, religious and ethical responsibility sometimes requires effort that is not immediately pleasant.
In connected recitation, حُجِبَتِ الْجَنَّةُ has a linking kasrah on the final t because of the following word. The verb's underlying form is حُجِبَتْ.