To dream of a cactus can suggest that you feel as if you are surrounding yourself with a hard exterior for some reason. The cactus is a plant which, according to biologists, actually started out as a bush, but through the process of adaptation and evolution, learned how to retain water very well and started turning their leaves into spikes in order to keep people or other predators from trying to steal the water inside of them, since they need it in order to continue to survive just like any other plant.
Perhaps you believe that you are surrounding yourself with the same type of protective exterior. Are you putting on a front with your friends and pretending to be someone you're not? Perhaps you are pretending to be tough when you really aren't in order to impress someone or in order to protect yourself from threats. Maybe you're pretending to have a much more cruel and cunning personality than you actually have? This type of dream can apply to any number of false exteriors you may be putting up.
The reason that you'd be having a dream like this though is because your mind is trying to warn you that you need to let go of this front that you are putting up because it is doing more harm than good. A cactus can afford to have needles surrounding it because a plant does not need to socialize with other plants; all it needs to do is protect itself. Humans are social creatures by nature though, and to cut yourself off from those that might want to try to be friends with you will only do you harm in the future psychologically speaking. Try to be a little more open and forthcoming about who you really are and make sure that they all see that you are serious and not trying to hurt anyone. Letting the real you out of your shell will be more beneficial to you in the future.
Dreaming of a cactus can also mean that you have out yourself into a prickly situation somehow. This is the type of situation where if you make one false move you'll end up hurting yourself somehow. And in many cases, even if the move isn't so false, you will still end up being hurt in the end. This is what it means to be in a prickly situation and there is no easy way out. All you can do when you have a problem like this is to simply push through it and accept the fact that you will have to go through a few hardships in order to get to where you want to be. This is what you must do if you really want to win in the end.
To dream of a cactus can also mean that there is something beautiful that you are missing because you can't see past the surface. Try to let your mind take a few more leaps and see where you end up at. This will be sure to lead you to future success and a more broad perspective on life.
The cactus is a strange plant in many ways and you are probably a strange person in many ways. You should subscribe to the philosophy that nobody is normal. It is perfect for you to sometimes act a little bit out of character and sometimes be a little quirky. It is even okay for you to feel a bit prickly. The only bad thing is when this happens all the time. Don't let this happen to you.