What is the damage? Due to?

There's no harm in washing your hair every day.
Use a good shampoo for that.
Conditioner after shampoo. During this steps, untangle your hair, it's easier... Harder during shampoo time, don't force else hair will break.
Serum/hair oil after hair is almost dry.
Dont rub wet hair with towel, blot dry.
Do hair treatment once a while for maintenance, at home or saloon.

If damaged due to chemical, best advice is cut off damaged part.

BTW, I have long healthy hair, wash almost everyday, swim twice a week at least. Colour my hair like maybe once a year?

Dry from chemical treatment? Like I say, if from chemical treatment, best to cut it off.

Trim off split ends, no harm drying hair with hair dryer, don't use too hot the heat though.blow dry till slightly damp only then apply hair serum to ends...

Be more proactive in doing hair mask treatment at home.