Sometimes I've said no to certain plans because at the time I didn't feel like going anywhere, but in general I don't usually do it, but we're not always in the mood to be with friends or others and just want to be alone for a while.
Whenever the condition is very favourable for me to go out and be with people, it's something that I will be willing to do because I am the kind of person that is loves being outside. I will normally find it very easy to associate with people than not associate with anyone at all.