Quitting coffee fits all the SMART characteristics (Specific, Measurable, Attainable, Realistic and Timing). SMART is an acronym that which helps to define important features when setting goals.
This is a great (and short) talk by Matt Cutts from Google where he talks about a great approach to cultivating bad habits. Just try something for 30 days. The thinking is that it’s a short enough time that it’s not overwhelming, but long enough to appreciate, and potentially extend, the new behaviour.