All cannabinoids are important, as well as the remaining terpenes and bioflavonoids.
CBD is extremely important, and not just when you use cannabis medicinally.
Mankind, as always, is too arrogant to understand the implications of its actions and fail to see its consequences when they perform such actions. THC breeding is one of them.
Breeding Cannabis for THC created an inbalance that makes it more harmful to people to consume it since CBD counteracts the bad effects of too much THC. Which is why you have more people with adverse reactions to Cannabis, and why many THC-isolated pharmaceutical drugs are so awful to so many people and it is why many medicinal patients prefer the whole plant.
CBD is cannabidiol, CBN is cannabinol, and CBG is cannabigerol, all cannabis plants contain these as well as THC, and many other compounds, albeit in different amounts.
There are also the terpenes which act synergistically with the cannabinoids and maximize its medicinal potential as well as providing the smell and flavour of its cannabis plant.
Which is why different strains have different smells, and the THC/CBD ratio relates to the potency of the plant.
If you don't manage sativas very well because it makes you anxious or too agitated, its because you need to change to a strain higher in CBD, usually indicas work better, or just change to a more balanced strain in terms of THC/CBD.