I admit that the company where I work in doesn't really have a strict rule about dressing up "well", so it's not just me who likes wearing t-shirt, sometimes.
I do nothing for my hair. It's half wet after morning shower yet not being tousled.
That shirt is actually a couple t-shirt - one is owned by my brother. It fits body perfectly and I match it with black high-waist pants.
(Couple) T-shirt : bought it online
Pants : wtf it's Zara Woman with inverted Z lol