First and foremost a marriage needs to be strong. There are many needs in a marriage for both partners and if they are being mutually fulfilled, then there should be little reason for a husband to stray.
I think it's important to have mystery in a marriage. It's healthy to take a break from your husband and pursue your own interests. Give your husband a chance to miss you. A little reasonable amount of distance is healthy not only for you but the marriage as well. And it's also good to be spontaneous. Marriage can get boring if it becomes a routine. So it's good to go on vacations together, randomly surprise each other with gifts, etc.
But other than these things, your husband is an adult. There are temptations everywhere and in the end your husband is going to do what he wants to do. You can't stop him. If a guy's gonna cheat, he'll find a way to cheat. Watching him like a hawk is not going to prevent him from straying. Rather, it would make things worse. There are beautiful huntresses everywhere.......but it depends on how strong and committed a guy is and how much he values the marriage and fears God. Can't stop him, watch him like a hawk, or breathe down his neck. There should be trust. Living in fear (although it is natural) is not healthy.
Besides how will you know if you have a guy worth holding on to if you don't let him go.......and allow him to demonstrate his faithfulness or lack thereof amidst all the pretty temptations?