ちりも積もれば山となる (ちりもつもればやまとなる): many a little makes a mickle; every little helps; even dust becomes a mountain if piled together

many a little makes a mickle; every little helps; even dust becomes a mountain if piled together

For small efforts or small savings that look pointless one at a time. Said to justify keeping at a tiny habit.

A Japanese proverb (ことわざ)