Devote is a strong verb. The sense is closer to persist in or hold fast to, the way you stay with something that is not currently rewarding you.
Which tells you Paul is not describing a good season of prayer. You do not need instructions to persist when it is going well.
There is a page at the back of a notebook, or a note on a phone, with names on it. Some have been there for years. At some point you stopped opening it, because it had begun to read less like a list of requests and more like evidence against the whole enterprise.
Being watchful is the second word, and it belongs to a sentry. Awake, looking for something specific. That reframes the whole practice. Prayer here is not only speaking. It is watching for the answer, which means expecting one to arrive.
Then thankful, which is the one that steadies the other two. Watching without gratitude becomes anxious scanning. You start monitoring God instead of trusting Him.
Paul writes this in chains. In the very next breath he asks the Colossians to pray for him, and what he asks for is not release but a chance to keep speaking about Christ. He is a man with good reasons to stop praying, still asking. Whatever else devotion means, it cannot mean waiting for circumstances to cooperate first. And if you have given up, you are in large company.
Devoted, watchful, thankful. Persistence, attention, and a memory of what has already been given.
Pick the prayer you gave up on. Open the page. Say it again today, and then actually watch this week for what comes back. Write down anything you notice, even if it is not the answer you asked for, and thank Him for it.