Most persons believe in simple and sophisticated lifestyle. Some also think that being simple can free from vague thoughts and give you peace of mind and also save your precious time while giving lots of tie to your look and dress and end up with a totally tired and worthless day. It is true that no one is going to subtract your marks because of your looks and dressing sense.
Consider a man on a working place with long weird and unpaired nails, wearing crushed trouser and shirt or a girl with uncombed hair and giant nails, wearing scratched or torned dress. What would be your reaction? An automatic universal repulsion from the first look. The phenomena of automatic repulsion doesn't apply on those having a good look and dressing sense. Dressing sense and looks is a part of your outer personality and contributes only 10% in your whole personality but this 10% is able to make or break your first impression on strangers.
"Beauty lies in the eyes of beholder", an old proverb so can't do anything if somebody has assumed that you are not beautiful but being presentable is in your command. Have you ever noticed that why in most of the places like schools, offices, working places, parties there are dressing codes, they are not just to make similarities of colors and dresses but to make people representable. Wear a formal dress and than notice your way of dealing with people and compare your behavior with the day you were wearing an informal, you can find a magnificent change. This is not because of the dress but because of the confidence that come up automatically after wearing formal or any nice dress.
Good looks and dressing sense builds confidence in you and its a very part of your grooming personality so please don't avoid that. Neat and clean dress, paired nails, combed hairs and aroma makes a positive atmosphere around you. Remember that don't misinterpret it with 'lookers' who wastes their precious time only on maintaining their looks but often becomes a 'laughing stock'.
Be in your own skin. Polish your outer personality a little and feel the change. This positive change can make you do much more things confidently than before.