Any messages on your instrument panel? "STARTER SYSTEM", "KEY NOT FOUND", or ???
Do you use your CRV every day? Or, did your CRV sit unused for weeks, then it wouldn't start?
As others have said, it's most likely you have a weak/dying/dead battery. But before you replace the battery...
1. Inspect your battery terminals for corrosion:
CAR BATTERY Corrosion — Causes, How-to Remove & PREVENT it
2. Check fluid level in your battery:
3. Simple test for dead battery in the key fob:
Bottom Line: Give us more clues & info -- tell us the whole story -- then we might be able to pinpoint the most-likely problem AND suggest potential fixes.