Should Stoics wash their hands?

One of tenets of Stoic thought is that situations you cannot control cannot themselves be evil.  To take just one quote among the very many the Stoics offer, Marcus Aurelius writes:

It is no more an evil to suffer change than a good to come into existence through change.

For example, if you get a cold, that is not evil.  It is merely a change, which should not disturb your tranquility.  This attitude seems a bit disturbing, though.  If it isn't an evil, why avoid it?  To continue the example, why would we wash our hands to avoid getting a cold, if that cold isn't a bad thing?

I'm not sure I have a good answer for this.  I'm just a beginner in Stoic thought, so it is quite likely this philosophical question has been answered elsewhere.

My guess is that we should in fact wash our hands, because it is part of the activities that will promote health, and working to promote good things such as health is a good deed.  But I'm not sure I completely buy this argument, because it seems to disassociate the practice and the desired outcome, when it is obvious to me that they must be linked.  It doesn't answer the question why we work to avoid something that is not bad.

Maybe we should just admit that it is bad to get a cold.  This seems fairly obvious to me.  But we shouldn't let things that are admittedly bad have a negative effect upon our mind.  This draws a distinction between a physical, objective evil and an emotional, subjective evil, and what Marcus Aurelius is talking about is merely the subjective evil.

Still, I think there's something I'm missing here.  But I'm still going to wash my hands.