Perpetually behind

Why does it seem like I'm always behind w/ lab work? It doesn't seem to matter if I stay late, or come in on weekends, or work at home at night; there is another project nagging at me. I have to drive 18 hrs to MT this week for a wedding (E is the best man), and next week I'm busy w/ something else, and then I have another wedding where I'm a bridesmaid. I'm excited about all the travel, I know it will be fun. In fact I can't wait to go! But I have this big ball of stress sitting on my chest. I didn't get my manuscript revised yet. (I realized I have a lot to do... more reading, more writing) I am falling behind on my schedule for the imaging work I set out for myself and I am enormously behind on my proposal.
Plus I need to go buy two B-day presents, find something decent to wear to the wedding this week, and get my bridesmaid dress altered. I'm running out of time!