1. Spoil yourself
When you feel like a big elephant, no pants fit you anymore, you're too tired to wash your hair and not to talk about putting on make-up: spoil yourself. Go get yourself a fresh haircut, do your nails, have a friend over to do your make-up, order home pizza and buy a dress that fits your belly. This is my favorite things to do on bad days when I'd honestly just want to stay in bed all day.
2. Plan the future
If you're tired of being pregnant and you can't wait to have your baby there with you, planning the "after pregnancy life" can help a lot. A little thing I do all the time is that I look at baby clothes online, plan the nursery and just visualize the time when the baby is actually here. It makes me super happy on days when I feel like it's an infinity of body pain and nausea left before the baby arrives.
3. Allow yourself to not do anything!
If you're actually having a shitty day, you're not in the mood to even try to fix it and get out of bed, well you know what? Then stay in bed. Allow yourself to "just be pregnant" and not do anything at all. Watch your favorite series and take naps every second hour. It's really okay to not be a superwoman 24/7 and keep up with everything. I mean, you're growing a human being inside of you!! That's superwomanich enough. You don't have to do 50 other things if you don't feel like it.