Stress Tolerance -

1. Discuss their awareness of their stress triggers. All of us have tell-tale signs that our blood pressure is rising and our anxiety is increasing.  Helping your employees know what their unique physical symptoms are will help them be proactive in removing themselves from difficult situations before they lose control.  
2. Provide group relaxation activities. There has probably never been a better time to consider sending a reminder out of health benefits they are eligible for under your health plan (gym membership, smoking cessation, etc) and bringing some healthy resources on-site: massage therapists at lunch, a walk club after work, a company sports team.  Even having live music brought in can change the mood and lighten up a stressful work environment. Or how about a Guitar Hero or Rock Band competition to blow off some steam? 
3. Discuss factors in and out of their control.  By helping people separate what they have a direct influence on (their attitude, their job performance, their pursuit of personal goals) and the things they cannot control (a merger or acquisition, cybergossip, a layoff) it minimizing worrying about things that may or may not happen. Help them channel the anxious energy into activities that move them closer to a goal or a healthier mindset.  

Flexibility -

1. Encourage them to take time to respond to unexpected events and not reject them out-of-hand. It is easy to have an immediate negative response to something we don't understand or want to have happen. A lot can be said for "sleeping on it" and the more time you give people to digest bad news the better. 
2. Brainstorm, preferably in a group context, to harvest ideas for handling dynamic, changing demands. Some members of your team probably have demonstrated a high level of flexibility (think of those unflappable folks who never seem to let anything get under their skin). Leverage the strengths of your resources and either try a group consultation or partnering members together for some mentoring. 
3. Use change as an opportunity to learn and develop; consider how past experiences and current skills are applicable to new challenges. Remind them of a past experience when a change seemed daunting and scary at first but resulted in some unexpected, but positive outcomes. What are the old processes or cultural norms that have been needing a face lift? When things are moving at high velocity speed they are the things we put in the "To Do" pile and hope to get around to them one day. One day is here. Open the file and see what positive learning can happen right now.