The best Quotations

It is a good morning exercise for a research scientist to discard a pet hypothesis every day before breakfast. it keeps him young.
- Konrad Lorenz

Do you know the writers of the following quotations?

Quotation No great deed is done by falterers who ask for certainty. - writer
Quotation Luck can often mean simple taking advantage of a situation at the right moment, It is possible to ''make'' your luck by being always prepared. - writer
Quotation In those days he was wiser than he is now - he used frequently to take my advice. - writer
Quotation The friend in my adversity I shall always cherish most. I can better trust those who helped to relieve the gloom of my dark hours than those who are so ready to enjoy with me the sunshine of my prosperity. - writer
Quotation Extremists think ''communication'' means agreeing with them. - writer
Quotation In short, luck's always to blame. - writer