Depending on how serious your asthma is you might try to adopt a regular exercise routine. Up until getting unwell I never felt better than I did after gradually getting fit. I really was in control of my asthma and not the other way around.
You said you lead a healthy lifestyle so I don't know exactly what to recommend but if you can fit 3-4 half hour jogs into the week then that's a great start. Any cardivascular work will gradually increase your resistance to the symtpoms of asthma. I know girls who don't like to run for reasons that I shall leave to your imagination, but cycling and swimming are almost as good (swimming especially, if you push yourself).
If you get ill then rest 'til you get fully better - I wish I had