Hi Rfc and welcome to the site. If you read around GT you will find the answers to stopping. Putting up barriers by limiting access to money, banning yourself from places or websites where you gamble and keeping busy with other things. Also getting as much support as possible – it is hard to do this alone.
As for staying stopped – that is indeed the hard part, but recognising that you cannot gamble again – that even one “free” bet can lead to a slippery slope is a first. Finding a new identity as a non-gambler, perhaps by picking up an interest you had before gambling or joining a non-gambling community can help.
But for now – put those barriers in place and keep coming back to your journal or take part in groups here to let us know how you are going on. I wish you well.