No, you haven’t wasted your time or money. So you ate some dessert & other treats over Christmas. It’s not Christmas every day & if you’ve recognised it for what it is (a special occasion exception) & gone back to eating as per your plan you’re fine. You’ll always be faced with these type of dilemmas (travelling, dining out, holidays, etc.). Over time we learn how not to beat ourselves up about it, make the best choices we can in the situation, accept it & move forward.
Part of the weight loss process is learning about your eating, what foods you can or can’t eat (or are or are t willing to eat) & how much or how often you can eat some foods. I described it as discovering what foods I could eat regularly, occasionally, rarely & which foods it was best if I avoided. I don’t eat sweet foods except at Christmas & certain special events - rarely. Some people work out they can have a small serve of say pizza with the family or they work out healthier ways of eating old favourites like a bun less burger - occasionally. I don’t eat high processed carbs like bread, pasta & rice - avoid.
Oh, and I’d lost about 68lbs at 6 months so not much difference. Seems like you’re pretty much on track. And the accelerated loss of the hair you would naturally be shedding usually lasts about 3months +/-. Your new hair is still growing just at it’s usual rate. Losing some hair, which regrew, was a small temporary price to pay for my weight loss.
You’ve got this.