Self esteem reflects a persons general opinion of themselves and their value (self worth). These opinions come from childhood, how a child is related to and how the world is viewed all have a huge impact on someones self esteem.
Over time these opinions about the self become entrenched and go on to effect all areas of a persons life . For example someone could feel like they are a failure which may get in the way of taking up opportunities.
Not being able to recognise your own worth can lead to staying in damaging relationships that match a persons distorted view of themselves. For example an individual with no self worth may find themselves being belittled by their partner which the individual feels they somehow deserve.