I know it's too cold for an ice cream, but I never can resist them!

Ice cream. Line Art from ArtMagenta.com
When you are sketching gesture drawings there is no time to make  aware decisions. The gesture drawing must be done in about a minute or two and during that time you only have one or two glances at the "model". So don't think while you are drawing. Just draw it, and afterwards get your time to analyze the gesture drawing.

Horizontal lines are very important for the image processor in our brain. When a viewer looks at the gesture drawing the horizontal lines must curve in a consistent way. Otherwise the gesture drawing will be regarded as bad or even incomprehensible.

In this gesture drawing my eye level is at the model's shoulder, where a horizontal line will be just a straight line, and above her shoulder horizontal lines are curved upwards and below her shoulder they are curved downwards.

Always take your time to analyze your gesture drawing when it is ready. If you do that, you will unconsciously correct such errors in your next gesture drawing.

And that is what gesture drawing is about. Exercise where you learn from your mistakes and always make better and better gesture drawings.