Fitting two weeks into one bag is easier than it sounds.
Pack around a small color palette so everything mixes and matches, and plan on doing laundry once mid-trip rather than bringing a fresh outfit for every day. Roll clothing instead of folding it to save space and cut down on wrinkles.
Leave a bit of empty space in your bag for souvenirs or items you pick up along the way. A packing cube system also makes it much faster to find things without unpacking everything at each stop.