Consistency one of the single most important aspects of continuous progress in strength training. When I refer to consistency, I refer to the ability to comply to an idealized model of training - a plan.
If you don't have a plan for your training, you need one. It doesn't have to be perfect and it can be changed as new information comes in, but you need one. If you're going into the gym and sporadically choosing exercises and weights, you will not make progress for very long. On the other hand, if your plan is to train 3 times a week, and you're only in the gym twice a week, you're not likely to make progress for very long.
Consistency has two primary effects.
First, it actually gets you to do the things that stress your body to cause an adaptation. It doesn't matter how good your plan is if you don't actually do it. The best strength specialists and nutritionists in the world can’t help you if you don’t do the workouts and diet programs they provide you.
Second, if you stick to a program, you know what's effective and what's not. Let's say that each week your training is planned drastically differently from other weeks. At 5 months into your training, imagine that you feel horrible and by all of your metrics of success, you are not making progress. How are you supposed to know what caused that with any confidence if the program constantly changes? You have only speculation. Conversely, let's say you progress wonderfully. Again, how are you supposed to know what caused that and how to replicate it for future use? You can't.
However, if you follow a consistent program with only single variable change, you will have a much better idea of what caused your progress or lack thereof. This will allow you to make predictions and modifications for the future based on what you confidently believe to be true. Will this be a perfect predictive model based on the inputs? Absolutely not, but it's far better than the multiple change method.
Set up meetings with one of the most important people in your life: you.
If you are true to your word, then you show up to meetings that you agree to go to. This might be a work meeting with your boss, a weekend away with your best friends, date with your spouse, or even just picking up your kids when you said you would.
With that in mind, allocate specific time to training that cannot be replaced with anything else and know that this is your time to work on you. You aren't beholden to anyone else at this time - just yourself. Keeping this consistent (5:30pm Monday/Wednesday/Friday, right after work, maybe?) can be extremely powerful in developing the habit of consistently training. If possible, this time should not be interruptible by others: work, family, etc.
Once it becomes a habit, you will have taken one of the hardest parts of training (getting in the gym) and made it easy.
Lack of compliance is the biggest killer of progress in the gym. Get a plan and stick to it. Schedule time for you.