What do you wish you'd known?


I am going to be a solo traveller and I’m interested to know what people wish they had known before they went on their trips, and only discovered afterwards…

What are you glad you did or didnt do?
Did you miss something in a town you wish you’d known about?
Did you pack something, and never used it?
Did you NEED something you didn’t pack and had to go in search of it?
What trip did you do and was it long enough or too long?

In particular, looking for different advice to what is already available on the board…share you experience so others can learn from you ‘mistake’.