The thin line between Self esteem and Ego

Whats Ego....its Aham....a self centric person has ego...whats self esteem.....its self respect.....a respectable person has self esteem..... an increase in self esteem gradually transforms itself into ego .....theres a very thin line that diffrentiates the two, yet there is major difference between them, one is considered positive and the other as negative. and usually in some scenarios these 2 words get interchanged