I feel purposeful when I am making or doing something useful.
That’s why I spend so much of my time crocheting beds for cat shelters. As long as I am doing something that benefits someone/something else, then I feel my time is not totally wasted.
That is also why I feel guilty when I’m taking time for myself.
There is also the issue of having a goal. As long as there is a goal, there is a purpose. With no goal, it feels as if I am just wandering through life.