Valerie,
The ability to say "no" without feeling guilty is something many of us have had trouble developing. Not saying "no" can really lead to frustration as we fall father and farther behind.
I have found that saying "not right now" works pretty well. I often let the person who asked for help know when they should check back with me. Sometimes their time frame does not match my availability, so they find other ways to accomplish the goal.
