Not knowing if this is a question generated for a male or a female I will attempt to answer for both individually as the solutions are very different.
For Men - Depending on the length of your trip but especially for 4-10 days here are some ideas.
Pack clean socks and underwear for each day, and from your shaving kit just you razor and blades. Hotel will have soap and shampoo for free. Shampoo makes good shaving cream as well so don't use it all up in the shower. Then only 1 shirt for each two days, and trousers for each 3 days. You can generally get two days wear from a shirt if you hang it up after the first day and let it air out same with trousers but you can usually get 3 days out of them. If you have to wear business attire take a dark jacket that will go with many different combinations of shirts and trousers. Wear your jacket while traveling. If you are going to bring/wear blur jeans during your trip wear them while traveling and pack your slacks.
For women: This advice is based on what my late wife would do when we traveled - Get the lightest suitcases you can find!