When they reach a certain frequency, requests for your time become disrespectful. If everyone else gets their activities completed and you don't, you have reached that point. There comes a point when you look at the people around you and notice that you are merely a device used to complete tasks. Your feelings, desires and dreams are of no real meaning...to THEM.
Don't get me wrong, they don't wan't anything bad to happen to you. But tell me, how different is that than the way they feel about the family pet or a favorite pair of shoes? Many people make the mistake of thinking disrespect has to be overt, brutal, loud or obvious. That type is actually easier to deal with. That person can be dismissed and all hostility and bad feelings travel out of your mind and life with their exit. But what if they are close to you? What if they are friends? Family? A spouse? Change is necessary. Either their behavior has to change, or their distance from you must. Sometimes, you really do have to think of yourself first. Sometimes, it's the first time you've ever thought of yourself first. It's about time isn't it?