There are several reasons why many people quickly jump into a relationship. For some, there is a need, perhaps created out of pressure, to be in a relationship. I can completely attest to the experience of having some friends and acquaintances ask, "Do you have a boyfriend?" or "Why aren't already married at your age?"
Perceptions of dating and relationships vary from region to region and evidently from culture to culture, but the idea that some people feel pressured into being in a relationship is observable everywhere, whether we ourselves notice it or not. If you're the only single person in your squad, you may start to feel as if you're slacking in the romance department, and you'd like to find a special someone for yourself as well. For other people, a new relationship fills the void created by a bad breakup. In both of these common cases, quickly diving into a relationship is not a promising solution, because it's likely to do more harm than good to those involved in the relationship.
In the first scenario, having a relationship for the sake of giving in to peer pressure and fitting in is not a good approach, especially if you're someone that has other priorities that you devote a significant amount of your time and effort to. The relationship is not bound to last, because there will be an imbalance in time and energy. Due to other responsibilities and priorities in your life, you might not dedicate enough of your attention to the person you're romantically involved with, and this is simply not how a healthy relationship works. If you find yourself in this category of people, remember that you should never feel as if you need to be in a relationship, despite what your family or friends tell you. Only you know what's best for you at the current moment. Trust that when you consistently focus on yourself, your needs and your goals, the right person will come at the right time.
If you feel that the second situation is more relevant to you, I would highly suggest that you take breaks between relationships. Investing yourself into a new relationship shortly after a breakup is also not guaranteed to be a sustainable option, especially if you've come out of a long relationship. In this case it's more likely than not that your feelings for your previous partner are still lingering and that you have not completely healed enough to move on to the next one. Again, only you can know what's the best approach and course of action when it comes to dating and starting new relationships.
To avoid any potential heartbreak, drama and other unnecessary stresses and burdens, take your time with your relationship, move at your own pace and be open and willing to communicate with your partner about how you feel and where you stand.