What aspects really affect your workout, for better or worse?

For me there are two really big things that have a huge impact on how well I can work out. One of them is the humidity. If I'm exercising/running outdoors or indoors with the windows open when it is very humid out, I start to feel like I'm dying in less than half the time it would take on a normal, clear day. Humidity kills my motivation to work out, it makes breathing so much harder, and ugh I just can't get a good workout in heavy humidity. The other thing is food. If I eat too much too close to when I start working out, I feel sluggish and a lot less motivated. If I don't eat a moderate portion at the right time--maybe 2 or so hours--before my workout, the workout is just not as good and I don't have the energy to push as hard.
One thing that helps me get a better workout is music. I definitely prefer doing cardio workouts with my ear buds in and upbeat music playing.

Oh, and I HATE doing intense workouts when the smell of cooked food is in the air.

How about you guys, what kinds of things affect your workouts?
What aspects really affect your workout, for better or worse?
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