Routine, in reference to prayer, means setting aside time on a regular basis in order to pray.
It could be first thing in the morning, lunchtime, right after work, or late in the evening. The time slot itself is not critical. It is fine to keep trying various times until you find one that works for you.
But, if you wish to have long term success, you must establish a routine and stick to it.
This is because prayer itself is not consistent. Some days will be incredible, and you will hardly believe how fruitful the prayer was, and how refreshed you feel. Other days will be dry, and leave you feeling empty. This is entirely normal.
If you are a beginner, be patient enough, and persistent enough, to achieve your first round of success. Concentrate on the idea that God wants a relationship with you every bit as much as you want one with Him. Pick a passage in the gospel, like this from Luke Chapter 15, where God makes His desire clear. Spend time with it in a routine until God brings it home to you. When He does, you will understand.
“Then Jesus told them this parable: “Suppose one of you has a hundred sheep and loses one of them. Does he not leave the ninety-nine in the open country and go after the lost sheep until he finds it? And when he finds it, he joyfully puts it on his shoulders and goes home. Then he calls his friends and neighbors together and says, ‘Rejoice with me; I have found my lost sheep.’ I tell you that in the same way there will be more rejoicing in heaven over one sinner who repents than over ninety-nine righteous persons who do not need to repent.”
Once you are successful, once you feel as if you have truly connected to God during a prayer session, you will be hooked. That connection is something you will want to experience as often as you can.
At least for awhile. Then, like everything else, it becomes commonplace. You stray without knowing it, and your routine breaks. It doesn’t bother you at first, but soon you are uneasy for reasons you can’t explain. Then you realize you miss the most important relationship in your life, and you come back to routine, seeking to re-establish what was lost.
If you are a veteran working your way back, remember the first days fondly. Recall the routine and the setting of your first successes, and re-invoke them. Remember the first phrase that allowed your breakthrough, and revisit it to restart yourself.
As you work your way back, rely on the routine that is proven to lead to success. Be patient, and persistent, as you re-establish.
Whoever you are, beginner or pro, routine is vital. It establishes your commitment to the relationship. It is, for anyone in a secular circumstance, the closest thing you have to a vow.
Promise yourself, and God, that you will be faithful to routine, and give your prayer the best possible chance to be productive.