Where the money goes
The extra cost usually comes from eating out every day and moving without looking at the price. One coffee becomes three, a short taxi repeats, and the “just this once” dinner costs more than the room. Solo travel is not expensive by definition. It gets expensive when every decision is made hungry or in a rush.
On the first day, write down what you want to pay for no matter what. Everything else fits under a daily cap. When the cap is clear, saying no to a plan does not feel like a restriction. It feels like part of the trip.