Try to identify what bothers you and address that issue.
Is it disrupted sleep from the long days? Get shutters or blackout curtains.
Is it too bright when you go outside? Wear sunglasses every time you step outside your front door, and buy a wide brimmed hat.
Is it your clothes? Figure out what would make you feel more comfortable and invest in your wardrobe. If you're not a summer person you probably don't like too much skin exposed, so loose, cool clothing in natural fabrics like lightweight trousers and thin long sleeved shirts.
Are you sweating too much? Use antibacterial soap on your feet and underarms and the best antiperspirant deodorant you can find. Wear cool cotton clothes. Have cool showers in the morning and before you go to bed.
Is your house too hot? Try all the tricks for making it cooler. Open all the windows first thing in the morning to let the air in and then close them before it gets too hot. Close the blinds or curtains during the day in rooms that get a lot of sun. Buy electric fans.
If your working hours are flexible and you can work from home, get up early, work for a few hours, then have a light lunch and a nap like people do it hot countries.
Make sure your handbag contains a hot weather kit. Big bottle of water, sunscreen, insect repellent, sunglasses.
A PP said we make the mistake of not investing in our summer wardrobes because there are so few hot days and I think that's true. But I think it goes beyond just clothes. Summer proof your wardrobe, handbag, house, car, basically your whole life, and hopefully it will be more bearable.