I expect to pass through this world but once

I expect to pass through this world but once;
any good thing therefore that I can do, or any
kindness that I can show to any fellow-creature,
let me do it now; let me not defer or neglect it,
for I shall not pass this way again.

defer: postpone; leave for a future time
fellow-creature: human being; brother animal(?)
neglect: fail to give proper attention to; ignore

Variously attributed to Stephen Grellet (1773-1855), William Penn (1644-1718) and others