["I don't think I'll be able to go to the lake this weekend, I'm pretty bummed out.", "Awww what's wrong? Maybe going to the lake will cheer you up?", 'Yeah, I wish I could, but I have to house watch my parents house this weekend! Bummer.']
That is a bummer! Well, you can go next time!
I don't think I'll be able to go to the lake this weekend, I'm pretty bummed out.