Sense of Accomplishment in Meditation

Regardless of a meditation's perceived *quality*, I feel that finishing a meditation provides some sense of accomplishment. Nowadays, I am experiencing great lack of motivation, and when I set the goal of meditation as '30 minutes', I stop half-way and feel that I failed. Knowing how finishing things provides accomplishment, would it make more sense setting *shorter* times which I can finish? **Is there such a thing as the momentum of accomplishment in meditation or even in virtuous activity in general?** Or, is such a feeling of success a kind of attachment, and problematic? Thank you