If you made a home gym and stopped using it, it's not necessarily your fault. exercising indoors can be harder than exercising outdoors. basically, exercise makes you hot, a lot of the energy your muscles make while you work out becomes heat so to cool down blood moves to your skin's surface this can help release some heat into the air around you, which will absorb the heat until it is the same temperature as your skin. but when you're inside that air stays in the room with you making it harder to get heat off your body, so your body is working harder to keep you cool than if you were going outdoors. unless it's blazing hot or super humid outside. research suggests that 10 degrees Celsius is best for long workouts. and that's probably colder than your home gym or outside depending on where you live, but while you move around outside you keep coming into contact with new air, making it easier for heat to leave your skin but also getting a huge fan for your home gym could ease the struggle a little bit.