The mishna in Shabbos 113a says that one is not permitted to make ones bed if the bed will not be used again until after Shabbos. We see from here that it is forbidden to prepare for something that will not be used on Shabbos. The Rabbis made this decree in order to protect the sanctity of Shabbos.
There are, however, some exceptions to this rule. The Shulchan Aruch 323:6 says you can only do dishes if you are still planning to eat at some point on Shabbos. Magen Avraham adds that you are permitted to wash ten plates even if you only need two. Since any two of these ten plates can then be used, it is considered that all ten plates were washed for the purpose of being used on Shabbos.
A second exception is brought by the Magen Avraham 302:6. The case there is the same as the mishna. If the beds will not be used until after Shabbos, but you will be using the room, and the unmade beds will take away from the decor of the room, the beds can be made. The same can be applied if having a sink full of dirty dishes is something that bothers you, the dishes can be done even if you will not be eating for the rest of Shabbos. This is provided that even during the week you do not let the sink sit full of dishes.
Another exception is if you will be caused some kind of a loss. You can put milk back into the refrigerator after shalosh seudos even the purpose of doing so is for the milk to be fresh next time. Since the milk might spoil a little, it is permitted to put it away. Likewise, one may soak dishes if by not doing so the dirt will stick and will be hard to get off after Shabbos.

Rabbi Tzvi Aryeh Hyman, Mir Yeshiva
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Shabat Shalom