Being consistent is a key factor to success. It applies to anything people want to be good at. The more often you practice a skill, the more it becomes habit and over time, the benefits of accrue. Over the last 25 years of training and coaching, I have seen people succeed and fail based on how consistent their training was. The failings I have had have come from a break in consistency. If someone really wants to live a healthier, more fit life, it is imperative they be consistent in their training.
When people join our training center, we often avoid the question about what kind of results they can expect. There are several reasons we skirt the issue, but the primary one is we would sound like a late night infomercial. (The key difference is that our claims are true) Second, it all depends on how consistent the client is. If someone cannot do some sort of work out 3-5 days per week, they are just treading water or not backsliding as fast.
Find a way to work out a little every day. Training at a high intensity level is a key to results but you cannot always make it into the gym or sometimes your body just needs a rest. I did a talk for some nurses at the VA hospital a few days ago, the key factor I stressed was consistency. Imagine how hard it is to get off of a 12 hour shift of being on your feet, moving patients and eating on the run. It is exhausting. The last thing a person wants to do is go to the gym. (It is also the first thing they need) One of the recommendations I suggested was to do 10 full range of motion squat every half hour or so. It is a start to getting people to move better.
Consistency requires discipline. It is hard to scratch out an hour and a half to go to the gym. (1 hour training and 15 minutes travel each way.) Getting to the gym for a structured and well balanced training program isn't always possible. People often have an all or nothing mentality. Nothing could be further than the truth. There is nothing wrong with doing an AMRAP of 10 minutes in your living room of only body weight exercises if you cannot seriously make time to get to the gym. Just have the discipline to do it.
Some times, people just need a rest day. A rest day is simply a break in intensity. Rest does not necessarily mean laying on the couch and playing PS3 - though enjoyable. Rest day often means ACTIVE rest. Maybe a walk, yoga class or the evil elliptical machine at your other gym.
Side note: You should have another gym membership. I recommend to people if they do three training sessions a week with us, they should be doing SOMETHING else two days. The key is to get 5 activity sessions where 2/3 are some level of high intensity work. Globogym memberships are CHEAP. Access to a facility is cheap, training expertise costs more.
We have been using www.beyondthewhiteboard.com for our clients since for several months now. The clients who use it and keep records of their training are far more consistently then those who don't. Part of consistency is being able to track improvements, PRs and scores. If you are tracking your performance, seeing improvements is is easier to be consistent with your training.
Train consistently, train intensely, eat right and rest properly if you want to be healthy.