When trying to open up your Chakras you have to be very careful and have a good understanding of all your Chakras before starting out. I've seen some people who try to open only one chakra and throw the others aside. For example if someone only wants their third eye open they will try everything to rip it open but that's bad because it could become over active and set all the other Chakras out of balance. So that's why I strongly recommend to try and open up all your Chakras rather than just one and I know that's easier said then done. Many people can also hurt themselves badly if they try too hard to open all of them because it's intense energy and actually an entire transformation of yourself because by opening up all your Chakras you are going to see the world in a different way. Be careful though many people who went through this got hurt because they themselves were inexperienced and their bodies weren't ready to experience such an intense opening of energies... so I recommend studying about all the different types of Chakras, seeing how your Chakras are currently aligned at the moment and looking up and studying "dark night of the soul"
You are correct in saying it is important to equally work on all of your chakras. An imbalance can cause the person to feel tired, out of sorts, ungrounded etc. However, a person cannot become severly hurt from attempting to open their chakras, as to an extent, they are already open and active. But it is important to treat them equally and also to read more on the topic.