Depends on what you're doing. Are you trying to lift to lose weight, or trying to lift to gain muscle? Or both? Or just to be generally healthy and not necessarily either of those?
No matter which case there's one thing I can say for sure though. Like Silent said, really dedicate yourself to it. Once you have and you're working out lifting w.e at a consistent basis it's quite satisfying once you start seeing results, which is very encouraging, but you've got to try not to let other shit get in the way and end up not working out for a week. Especially if you're lifting weights. You can lose quite a bit of muscle in that amount of time surprisingly, though it's much easier to re-gain than it is to gain initially. I haven't been lifting weights or doing cardio outside of some sets of things here and there that I do every day, but not an actual workout. Like a set or two of bench flies/dumbbell presses, set or two of chinups/pullups with 8 - 12 reps, set or two of pushups from 10 - 30, at least 100 situps, sometimes with 20 - 40lbs weights, set or two of curls, etc. Sometimes I don't do that all at once though, sometimes I spread that throughout the day and I'll do it on top of an actual workout as well as long as I don't feel like I'm straining my muscles too much. And that's a fairly decent amount of shit to do, but the past week or so I've been doing much less than I normally would because of how completely tired I am from other stuff (not my workouts), and because I started getting migraines after doing cardio occasionally. Basically really fucking sucks, but I still haven't even completely stopped exercising and I've lost a noticeable (at least to me) amount of muscle from my biceps. So yea, if you start, really try not to stop even for a short time, keep working out at a consistent rate. And if you don't start, then fuck you start.
Also if you're trying to lose some weight as well really try not to focus too much on dieting. You can focus on healthy eating obviously, and well should actually, but if you're eating fewer calories than you should be to maintain your weight level then be extremely careful. If you're not eating enough working out is a lot harder and a lot more dangerous. Way more likely to pull a muscle or at least strain them too hard as you'll have a lot less energy and will probably be a bit more reckless. Plus it's simply not effective, you need fat and carbs to build muscle so more or less eliminating that is a bad idea for the weight loss and the muscle gain.