Bread is super annoying in this regard. I eat a single slice every morning for breakfast, which means I can't go through a whole loaf before it starts getting moldy, or at least stale.
Freeze it. If you eat toast in the morning you can toast from frozen.
Bread freezes very well. It also thaws out really quickly. Or you can just stick the frozen slice in the toaster.
If you go to a supermarket where they bake bread, and they have whole loafs of in-store baked bread, they'll often be happy to sell you a half-loaf. Just take it to the bakery counter and ask if you can buy half the loaf.
Yep, Whole Foods does half-loaves.
Bread remains fresh longer if you slice it on demand rather than in advance. Keep it resting on the sliced side for maximal freshness.
Then maybe double it and eat 2 slices; problem solved.