Some of your most important contributions will look small to everyone except the person who needed them.

Scale is relative to need. Something that cost you an afternoon can be the thing someone else remembers for twenty years, because it arrived at a moment when they had very little. You will usually never know which of your actions did this.

Since you cannot identify them in advance, the practical response is to do the small helpful thing more often rather than saving effort for occasions that look significant. Most of the significant ones do not look it.