Use fans in the summer. You can keep your thermostat at 77-78 during the day and still feel comfy. The issue of why you feel hot is not because 77 is hot, it’s because air is not moving. Having a fan on keeps the air circulating in your apartment, making it more comfortable without using too much energy; instead of relying on your AC to move air around by lowering the thermostat so it keeps turning on.
Blackout shades also work to cool down your apartment, not just keep light out. Put them on windows facing west to keep sunlight out during the hottest time of the day.