Some services have limits for how often you can use them with IFTTT. If you check your activity feed and see an error message that reads "usage limit exceeded," then you have hit one of these limits. Some examples of these services are Twitter, Blogger, and the SMS service.
We try to make this as transparent as possible, and let you know when you’re approaching a limit and when you’ve hit it. If you hit a daily limit, your Applet will start working again the following day.
We would recommend configuring your Applets so that they run less often to avoid hitting these limits. You can do this by choosing different criteria for your Applet to trigger on so that it runs less often.
IFTTT's rate limits can be found here.