What can you do to keep your energy levels up? Some women are a lot more tired during pregnancy, so taking care of yourself and managing your energy is important. Getting lots of rest and sleep is important for your health and the baby's, and helps lessen the stress of everyday life. 
Nothing currently available from a physician improves uterine blood flow better than real rest. Peter W. Nathanielsz 
The Gleaners 1857 by Jean-Francois Millet
There are good lessons in all this for the good management of a pregnancy. Regularity of habit - eating, sleeping, work, relaxation - will give the baby a better chance to develop normally.
Peter W. Nathanielsz 
Not that long ago, when people did work and chores, they had a song for everything. They hoed the garden, chopped trees, swept the floor, cleaned the house, to the rhythm of the song, in regular, rhythmical movements. Even if you don't have a song for everything, finding a rhythm in any task you're doing can be more fun and a lot less tiring.
Finding a rhythm in the structure of the day can be very helpful too, such as eating meals and waking and sleeping at regular times. This saves you energy for going through the day, especially if you are working a lot or if you already have a little one. It also helps to prioritize and simply rest when you can!
 Lee, Kathryn, RN, PhD, FAAN and Caryl L. Gay, PhD Inadequate sleep in late pregnancy may influence labor and delivery University of California UCSF School of Nursing, 15 December 2004, June 2009 < http://www.universityofcalifornia.edu/news/article/6819>
 Nathanielsz, Peter W., M.D., Ph.D. Life Before Birth and A Time to be Born. Promethean Press, Ithica, New York, 1992 page 160
 Harwood, A.C.. The Way of the Child. Rudolf Steiner Press, London 1974
 Nathanielsz, Peter W., M.D., Ph.D. Life Before Birth and A Time to be Born. Promethean Press, Ithica, New York,
1992 page 141