First impression is the event where one person first encounter another person and forms a mental image about him or her.
First impression is something hard to change if you give some one a bad first impression believe me they will stick on the mental image of yours for quite a long time until they have the opportunity to know you better. This is relatively important when you are going for some interviews either for your scholarship school intakes or job. If you give those interviewer a bad first impression they will give you a very low marks even you are graduated from Harvard or Cambridge with first class honour.
In a nutshell always give people a good impression on you! Take care of your behaviour personal hygienic and dress properly according to the situation and you will be just fine.
