A reason to know, love, and serve God more... with the help of his grace of course.
The more we do for God here, the greater will our happiness be in heaven. Now while everyone will be perfectly happy in heaven, some will have a greater capacity for happiness than others.
A quart bottle and a pint bottle may both be full, but the quart bottle will hold more water than the other. Two people may gaze upon Raphael's 'Marriage of the Virgin' and both be delighted at the artwork. However, the one who knows more about paintings would be able to appreciate it more.
∴ More love, more happiness...
Ref: The Faith Explained by Leo J. Trese