Attachment means clinging to something obsessively, unable to let go of it. If you care too much, and take things or whatever is related to you too seriously, be it ideas, people, affairs, or objects, then that's attachment. As a result, you will be constantly stressed. From the Buddhist perspective, attachment results from regarding oneself as the focal point. Attachment shouldn't be explained as persistence, or will power. If you persistently maintain your direction and your aspirations, if you hold to the goal and conditions of your endeavor, that is good.