Whether or not stress till overwhelm your coping abilities depends on the intensity of the stress, the duration ofit, and your susceptibility to it.  Very often the stressful event that damages you in a minor "last straw" event at the end of a series of difficult happenings. 

Excessive stress and failure to cope is the major cause of mental illness and many physical illnessess and is a major factor in all disease. 

How susceptible to distress are you? 

Is your life situation basically happy? i.e. satisfying work, friends to confide in, good physical health.  If not, a relatively minor stress can precipitate a crisis. 

Do you have to adapt to a number of changes at once?  It is usually easier to take change one at a time. 

What are your limits? What inner resistance do you have? Experience and heightening of self awareness helps here.  Know yourself. 

Timing is important. Something that does not ordinarily bother you can explode you at a sensitive time. 

If your life is generally solid and secure you will have a better chance of withstanding wear and tear.  If you are already on shaky ground, you will be easily overwhelmed. 

It also helps to know your normal cyclical rhythms, menstrual and otherwise.  When you do not flow with your rhythms and moods you will be more susceptible to distress.

How to know if you are overstressed: 
We don't always know whether we are under stress ornot.  Maybe you have been carrying a load for so long you ar no longer aware that you are under tension. (The function of tension is to numb pain.) 

It is difficult in this complex distracting world to be turned into yourself with all the stimuli pushing and pulling you this way and that and knocking you off balance. 

It is important to learn to tune into yourself, to relax with yourself and to listen to the messages your body relaying to you.  Body awareness techniques such as focusing your attention on different parts of your body during deep relaxation can be tremendously helpful.  Try to be quiet with yourself and "hear" your body at least once a day, for at least 15 minutes.  Illness is described in oriental philosophy as lack of balance between positive and negative electrical energy in the body.  Balancing your body energy through centering develops an awareness of this and can correct disharmony or dis-ease (lack of ease).  A healthy body is supple, strong, and energetic. 

Learn to be more in touch with yourself, more honest and accepting of yourself as you are.  You might need to get through the armoring of your defence system.  As you peel off the layers (like getting to the core of an onion) at each layer you will uncover the pain that put it there whileyou also increase your capacity for joy.  Between each layer of release and pleasure there is a layer of resistance and tension.  Do you realistically need all those defences now or are they a result of past conditioning or present misperception? 

Ask a close friend if you seem more uptight than usual.  Pick someone you can trust to be honest with you.