Life is struggle

Sometimes I feel that the second name of life is struggle, struggle n more struggle. Yes it's true, whenever you wants to do something good things u always fail. Still we try to do good things but get nothing. Why everyone says do good and you will get good? It seems to me that this is not true. When you do something good, then it should be good with you too. But why doesn't this happen?All these things frustrate me a lot.