The common cold isn’t a lifestyle decision. Getting a cold isn’t being an intravenous drug user or having unprotected sex with high risk individuals.
In the case of blood transfusions your statement rings true.
The hell it isn't. There are plenty of behaviors that predispose you to catching or spreading a cold: associating with large numbers of other people is very often voluntary and avoidable. Going to a concert, a bar, or a theater will expose you to lots of other people. Choosing to go see a movie each week, regardless of the consequences, is a lifestyle choice.
Washing or not washing hands may not seem like a "lifestyle choice," but it's really not a lot different than choosing to use or not use a condom.
People can take sick days or choose not to, they can apply for jobs in risky environments (e.g. elementary schools, hospitals) and they can choose in some cases to telecommute.
All of those decisions are in some senses lifestyle choices, and all have a huge effect on your chances of catching or spreading a cold (or flu or other such ailment).