How can a Man, idealist by nature, lives in this imperfect world so that he may be chosen for Paradise?

This is not a contradiction. As far as your being is concerned, you must live as an idealist. But when you are amidst others, then you should be pragmatic and accommodating. If someone is pragmatic for self-interest, that is evil. But when we realise that we cannot abolish God-given freedom and adjust with that, it is a form of worship. The only point of caution is that it should not be done for one’s vested interests but for disseminating the Word of God.