I think getting along with your cousins is one of the most important, and most beneficial, things you can do in your lifetime. Just hear me out, now.
Cousins can be just family that you see around the holidays, yes, but they don't have to be that alone. Why would you want that? I understand that, obviously, sometimes there are tensions or extenuating circumstances within a family that can cause a rift of sorts. However, if you can, I would highly recommend becoming as close with your cousins as possible. Especially if your mom/dad is close with their sibling of which the cousins are from, you'll be seeing a lot of them. It's the perfect opportunity to create a close friend for life.
A cousin-cousin relationship can be whatever you want it to be because you both get to make it and develop it throughout your entire lives. A cousin can be the person you stick with at awkward extended family gatherings. He or she can be the person you call when you're upset at 3 AM, or when you're excited for no reason at 12 PM and just want to talk to someone.
They can be the brother or sister you never had, and even though sometimes they might feel like the one you never wanted, it is well worthwhile to stand by your cousins through everything because you know they would do the same for you.
When you are young, sleepovers with your cousins are sometimes better than a sleepover with friends. You watch scary movies that you don't want to watch because everyone says that they aren't scared, even though everyone actually is and no one wants to admit it. There's also always the plentiful opportunities to poke fun at your parents. Of course, you can do those things with friends too, but something about it just seems better when you're with family. Your eyes instantly light up when you hear that they are going to be at that family party too, because even if you do not know anyone else there, you know you can always count on them to have a good time with.
As you grow up it starts to develop into a real friendship, not one that is forced. You want to see them, and you make plans together, no longer because you are forced to at family events. Even if you fight, there is a good chance you'll get over it and move on soon because you see each other all the time, and it's not worth it to fight over small things. (This is true with all friends by the way!!!!)
I love my cousins, I love the relationship I have with them, and I wouldn't trade it for anything in the world. And if I had to do it all over again, I absolutely would do it the exact same way.