Those beset by sloth generally generally avoid spiritually good acts. They don't pray; they attend Mass inattentively, possibly irregularly. It all seems like a lot of bother, and for what?
If they resolve to pray five decades of the Rosary each day, however -- and if they follow through -- they will find that they have taken on a relatively light burden. Call it fifteen minutes for someone who doesn't want to linger, everything nicely regimented, never a question about what to do next.
Even if the mind wanders, even if there's a sense of frustration or that it's all been a waste of time, when the last prayer is prayed, it's done.
What such a person who sticks with the Rosary will find, if he looks for it, is that the Rosary is not at all oppressive or wearisome or a cause for sorrow. He may need to adjust his own expectations of what he'll get out of this devotion, he may not understand right away that what he puts into it determines what he gets out of it.
But he will have developed a habit of spiritual good. He will have demonstrated to himself that the thought of loving God needn't cause sorrow. He will find that he has the capacity for charity and that making use of that capacity isn't as wearisome as it once seemed.