Could you walk away from a relationship, based on suspicions?

What would make you end your relationship?

If there is not actual infidelity, no fall outs, no nastiness. If you get on really really well, if you really love your s/o and can’t imagine ever being apart, what would make you end it?

If your s/o was secretive, private, keeps themselves to themselves. If you were suspicious as to why, what, they were doing. Could you, should you, be brave enough to leave?