来日方长 láirì-fāngcháng

[There are many days yet to do that;there will be ample time ahead; there'll be a time for it] 将来的日子还很长。表示事情还大有可为

曼思故国,来日方长,载悲黑奴前车如是,弥益感喟。——《鲁迅书信集·致蒋抑卮》