If you love art and have creative flair in your blood, or love music in all its forms and is part of your soul, then these can seem like an extension of rest and recreation rather than hard work.
However, if you don't have that ability, they will seem like the hardest subjects ever with the highest workload and worst results outcome.
Change the subjects for maths and physics and the same applies.
One persons hard work is another's walk in the park and everyone is different. If you are good at something and you like the subject, you will find it easier. Pick a subject you loathe and watch the motivation evaporate into waste of time.