If we want to do something but cannot, then before God, Who knows our hearts, it is as if we have done it. This is true whether the intended action is good or bad.
The most important thing during illness is to offer to God patience and thanksgiving for His merciful visitations. Sickness purifies sins and gives one time to meditate on the past.
In everything we do, God looks as the aim, whether it is for Him or for some other purpose we act. So, when we wish to do something good, let us have as our aim not to please men but to please God, so as to have our eyes always fixed on Him, doing everything for Him, lest we bear the labor but lose the reward.