In some ways adult stress is a continuation of teenage stress. How we deal with pressure in our adult lives is greatly influenced by what kind of personalities we have formed.
People who pay attention to who they are and who they wish to be will have less internal conflict and more clarity when it comes to dealing with external pressures. People who just let their environment form who they are will just keep succumbing to pressure - continuous, ongoing stress creeps in much more easily.
Much of adult stress is a result of rigid self-image; it is the thought that life has to be lived only the one, predetermined way. With such a way of thinking taking a look around and noticing many different solutions is very difficult.
Adult stress says "I have to do this." It is quite backward, but for many people stress is a way of validating their existence without taking the strength to deal with issued deeply important to them. Subconsciously they think that if they suffer, suffering must be valuable, and therefore their lives must be more meaningful.
Dealing with adults stress is twofold: first, conscious decision-making is helpful for overcoming and reducing day-to-day stress, and secondly, in the long term overcoming any deep rooted issues will help convert pressures of stress to pressures of fulfillment.