I feel guilty about taking a break from therapy or practice.

That guilt arises precisely because you're serious, and it's not that you're doing anything wrong. In common: rest isn't "slacking"—it's necessary for both the child and the parent. Overloading can wear down the child's motivation and the parent-child relationship. The effect of therapy is supported more by "being able to continue without strain" than by "attending without missing." What the family decides: the balance of how much to rest and how much to push is yours to set. A guide: "isn't the family worn out?" "is the child enjoying it?" Taking breaks is an important part of continuing. Rather than guilt, value the family being able to smile.