Should I force myself to do a 'fun' and harmless activity with my friends because they want me to do it, even if I don't want to do it?

You should always listen to your feelings. If you don't want to do what they're asking you to do, because it makes you uncomfortable then don't. Try to understand what they are asking from you and why you don't want to do it. Maybe telling them why you don't want to do it will make them understand you and they will stop pushing you. Don't let anyone force you to do anything you don't want to do, even if it as a harmless acfivity. But maybe if you are feeling down but you don't want to do anything fun you should try to ignore that feeling and go have fun, maybe eventually you will enjoy it!

no, if you do not want to do it you won't enjoy it. you could try to tell your friends you don't want to do that and then you could maybe suggest something you might all enjoy for the next time you plan on hanging out. however, take into consideration the fact that they need to enjoy it also. and maybe make the exception to help them out and go with them. but make sure you aren't settling and never doing anything YOU would like to do. that would for sure make you unhappy, and you don't want that and they don't either

Absolutely not. No one should ever let peer pressure get the better of them. People have the right to say no to this that they don't want to do. If the people you are hanging around with make you do something you don't want to do then they aren't the right people to be around. There are so many better people in the world that won't make you do something that you aren't comfortable with. You just have to put yourself out there and find them. It can be scary to do that at first but it is way better than being around people who will disrespect your boundaries just because they think they can.