How can you possibly say no? You know and understand that your friend has been stressed out and needs cheering up, and you'd really like to help them as you hate seeing people sad. And if you don't go just so you can relax, does that mean you're selfish? How can you choose what to do? Take a read
Knowing When To Say No Can Transform Your Business (Or Life!). When you say no, you are inadvertently saying yes to something else. Make your choices wisely, protect your time - it's your greatest asset!