Many times we have a hard time saying "no" to people. And sadly it can come at our own expense. For example, a mother will ask her mother if she will take care of her child, after all, Grandma loves the baby. And Grandma says, "okay" and then calls her friend she was going to go shopping with to cancel. And resents her daughter.
If saying "Yes" is going to inconvenience you, it doesn't have to be hard to say "No".
Here are some ways to gracefully say no without making yourself and others feel bad.
1. Explain that you have a lot on your plate right now
Most reasonable people will understand that you have other responsibilities. If they push back and insist that you help them anyway, fill them in on what you have going on.
2. Let them know you will get back to them when you finish what you are doing
People will often ask for help immediately. Politely let them know that you are busy at the moment but will be happy to help them when you finish what you are doing. If they are reasonable, they will understand.
3. Let them know that you will think about it.
You're really giving them a "Maybe" instead of an outright "No". If you really want to say no, say it. Take the time you need to think about the request and if it is something you can help with. Just don't forget to get back to them when you say you will.
4. When dealing with salespeople politely let them know that the product doesn't meet your needs
No reasonable sales person should be able to fault you for saying this and take your answer personally. If you add that you'll reconsider their offer if things change, they should leave happy.
5. Refer them to someone else who would be a better person to help them
This way you're not saying "No", but giving them a better option which should make them happy.
6. Let them know that you would love to be able to help them, but...
This is a much more encouraging way to say "No". You're letting them know that you would like what they are offering you to or to help them but at the moment you don't have the time to help or the need for what they are offering.
It may be scary to put any of these options into practice, but the more you do it, the easier it will become and your life will be better for it. And if you are sincere and honest in your refusal, people will respect you for it. They may not always like it but they will respect your position.