You can control how good a job you do, but when you invest in your employing company you're also investing in the job all your co-workers do, and more important

You can control how good a job you do, but when you invest in your employing company you're also investing in the job all your co-workers do, and more importantly in the expectation that your customers will keep wanting to, and be able to, do business with all of you. Diversify.