Neal, racing to Berlin one day, and back on the next sounds like horror to me: stress pure. I would skip that or would not plan a big program there. If museums are your interest, then pick one, or two at best. I personally have no interest in tourist "attractions" at all, and certainly not in mueeums, instead I would check for the "centre of gravity" in a city, of which there can be several in a big city, and then simply stroll around there, inhale some of the ambience, look for a restaurant that seems to invite me, and observe the flow of life, and how the locals are moving, maybe following the unexpected sidestreet suddenly opening to my eyes... Many historic places have been mentioned in earlier posts, but believe me - they look for the most very ugly, and not really interesting. The Brandenburg gate for example is tiny and boring and hopelessly overestimated, so is the Alexanderplatz, and the Fernsehturm really only is interesting if you visit the restaurant and enjoy the view from up there - but do not be mistaken, from up there you see a huge panorama of small details that will not give you a real impression of how Berlin looks like when you walk its streets. Checkpoint Charlie and remains of the wall are okay if you think you owe that to your tourist diary, but a great experience they are not. Monuments and museums - don't you have that in Houston? You cannot get the atmosphere of a foreign place by walking around in monuments and museums.
Honestly, I would not recommend Berlin at all. It is beyond me why foreigners always want to go there. There are more beautiful places in Germany. Also, places that are not as dirty as Berlin.
Relax. Keep it easy, don't pack too many dates into your organiser. Do you want to
enjoy a travel, or do you want to set records for marking checkpoints on a list? If you realise that you have to hurry to keep up with your plans and time checkpoints, then you have planned something wrong, I would say. I mean you do this for private enjoyment, not professionally, yes?
So: no hectic!