Comparing ourselves to other people can be something that pushes us forward. However, unless we're really secure in who we are, it can be something that piles pressure on us. When we look at others and only see the ways in which we're not as good as them, it can affect the way we think of our own value. Comparing our looks, exam results, families or social media following to other people's can just increase our feeling of not being good enough. We see this in the story of King Saul and David, when comparison led to jealousy that ruled Saul's life.
God created us all unique, with different gifts, skills, appearance and, most importantly, purpose. You were created for a purpose that is different from your friends', and the more time you spend trying to be like others, the less time you have to fulfil the purpose you were made for. Don't get so distracted by someone else's race that you forget to run your own! It's about beating your 'personal best', not competing with others.