Make it a priority even if you only can have a few moments. If your mind wanders, pray for what your mind has strayed to. Read the Bible and meditate on what is said there. That will help your concentration. The answers to doubt about prayer are to be found in the Bible and in our experience.
Practice brings assurance.
Keep a record, a prayer journal, to remind you of the goodness of God. No, not yet. No, because I love you too much. Yes, I thought you'd never ask. Yes, wait until you see what else I have for you.