Keeping your balance is a must in any good self defense attempt. If a light breeze can blow you over, you should consider doing exercises to improve your balance and coordination.
Here are a few example of things to do to help you achieve this task.
As always choose the level of intensity that is appropriate for your skill level. But keep on challenging yourself to increase that skill level all the time.
Good balance makes just plain common sense!!!

You don't have to spend a lot of money either. Most of those things you can do at home with no specific piece of equipment.
Pogo balls are inexpensive and work great.
Can't afford a big exercise ball? Go to Walmart and get a $2 ball in the toy department. Also works great
Don't let excuses get in the way of bettering yourself!!!