Consequences of the fall of Constantinople

1. The influx of Greek scholars into the West propelled further the Renaissance.
2. European military advances were fuelled by constant Ottoman threat.
3. As the main overland trade link between Europe and Asia was severed, more Europeans began to seriously consider the possibility of reaching Asia by sea.

Christianity - language and culture schism

"Many other factors caused the East and West to drift further apart. The dominant language of the West was Latin, whilst that of the East was Greek. Soon after the fall of the Western Empire, the number of individuals who spoke both Latin and Greek began to dwindle, and communication between East and West grew much more difficult. With linguistic unity gone, cultural unity began to crumble as well. The two halves of the Church were naturally divided along similar lines; they developed different rites and had different approaches to religious doctrines. Although the Great Schism was still centuries away, its outlines were already perceptible."

More here.

Decline of an empire

As one Ummayad chieftain responded to a question about the reasons of the decline of their empire: 

"Rather visiting what needed to be visited, we were more interested in the pleasure and enjoyment of life; we oppressed our people until they gave up and sought relief from us, [...] we trusted our ministers who favoured their own interests and kept secrets from us, and we unhurriedly rewarded our soldiers that we lost their obedience to our enemies."

Ancient symbols