You’re doing great Phil 
Dan wrote a wonderful post about the phases you go through in sobriety. Feeling a bit down but not knowing why might be an early onset of the ‘pink cloud’ dissipating. You’ve got a nice few sober days on your clock now, sober life is the norm. I’m just behind you at 57 days AF days, and I’m already starting to think / prepare for the sobriety ‘novelty’ wearing off. It’s not a novelty of course, but that ‘yeah, I’m doing this!!’ feeling starts to wears down. When this happens, you have to double down on your efforts, ensure you remember your ‘why’. I think it’s a dangerous phase, because silly notions like ‘ah sure, one drink won’t do any harm’ can start to sneak in. You’ve gotten used to sober life, might even be feeling a bit bored. All it takes is one slip, then it’s down a rapid spiral to the old days of your active addiction.
I’m going through Dan’s post at the moment, and it’s fantastic read. You should have a look over it if you haven’t before / not in a while