Have the right reason to say NO

My work involves saying a lot of NO to my colleagues, stakeholders, my team and sometimes my boss. I am always prioritising and re-prioritising all the time and I have to say NO to a lot of ideas that I get. Few dos and don'ts that I have tried to come up with to save myself years of friendship and professional respect.

1. You don't say NO because you don't like the person who is saying yes to the idea. Your job is to make sure you are saying NO for the right reasons and not get biased from where the idea is coming
2. You don't say NO to an idea just because it was tried many years back and failed. Time is a big variable in product success equation, be open to relooking at interesting ideas
3. You don't say NO just because there is no recorded data to support. Many ideas originate from deep consumer insights and are often difficult to support with data. These are specially the ones which brings delight to consumers
4. You don't say NO to just to protect the team. Your job is to protect the customer not protect the team

At the same time,

1. You don't say YES to an idea just because it is coming from someone who has not contributed for a long time
2. You don't say YES to an idea just because it is coming from the top without much evidence on the ground

Lastly, communicate NO with candor and with genuine intent to land the communication with comfort.