It means did he regret what he did as a young man. Hard to say more without the complete context, but perhaps as a young man, he had 'adventures' which could be something as simple as things that young men do that seem crazy or dangerous when you look back on it ("I can't believe I did that!") to 'adventures' meaning something more like having an affair with an older or a married woman or something less frivolous than having a crazy all-night party on the beach

Thank you! "Cakes and Ale" Yes, I think he regrets that he had relationships with women before, because his current wife is just superb!

The meaning is somewhat ambiguous. It could refer to his younger years in which he behaved in ways that may have caused him to miss out on the life he currently enjoys - his lovely wife and comfortable home. Perhaps he was reckless and unfocused when he was younger? Maybe he had multiple casual relationships with women who were not as esteemed as his wife? One would need more context to know exactly to what "regretted his early days of adventure" refers.