Do you know how to judge people?

Do you know how to judge people? do you judge people correctly all the time?i dunno...for me, i always judge people wrongly... someone that i think is good and nice in the end i will find out he/she is bad...someone that i think is bad but in the end i will find out he/she is actually quite nice...i think it is quite dangerous if we cannot judge people correctly.... someone may approach us just to make us fall but we might not aware of them just because we thought they are sincere to us.....someone may try to help us but we refuse to accept their assistance just because we thought that they are evil and they are trying to harm us....in the end, we are actually giving more opportunities for those who want us to fail to harm us...can you understand what i mean?so, you think it is dangerous right?we might be in trouble but we can't sense it completely... can understand right?