The American colonists had become accustomed to doing a number of things, some legal, some not.
Economically speaking, the main things that they had become accustomed to doing were illegal. Specifically, they had become accustomed to being able to smuggle with relative impunity. The Navigation Acts were not very well enforced and the colonists brought in large quantities of goods from European countries other than Britain and from the colonies of those countries.
Politically, the colonists had become accustomed to having a great deal of self-government. While they did have appointed governors, they also had colonial assemblies that held the power of the purse and could, thereby, generally control the governors. They had also become accustomed to such things as the right to jury trials conducted within their own towns.
These were the sorts of things that they were accustomed to and which Britain began to take away after 1763.