In tough times, your competition is going to get their business anywhere they can--usually by attacking your best account. They have a special advantage--you've already solved the major problems so they can take it over at a lower price to maintain your solution. They also have a disadvantage--you are the incumbent with an existing relationship and it's painful for accounts to change. The question is which outweighs the other? If the latter is the heaviest then you win; if the former, then you lose!
What can you do?
1. Stay very close to your best clients--the ones who you think you can never lose.
2. Explore new ways to bring new value, to solve new problems, at your best clients.
3. Consider a preemptive price reduction before they ask you for one.
4. Expand your network of sponsors and champions inside your best accounts.
5. Start selling their replacement today (just in case).