First of all, don't worry!
It's good that you have such a good relationship with your Dad! Of course he's going to miss you as much as you miss him.
Why don't you slip a goodbye card or message into his case or bag or jacket pocket, I used to do that when my Dad went away so he'd know how much I missed him, and I always felt better knowing he'd find my letter when he unpacked.
You can call him every day remember, or email, or text! There's so many ways you can stay in touch, maybe he can even send you a postcard as something to look forward too?
15 days will go by in a flash, he'll be back before you know it! That's just over two weeks remember, hardly anything!
In the mean time, why not do some fun stuff with you friends to take your mind off it, go and see a movie or have a sleepover, or spend some time with your Mom?
And you can visit your Grandma as much as you like. Why not make her a Get Well Soon card with all of her favourite things, or buy her something she likes, like flowers or chocolates?
She knows you care I'm sure, and I'm sure she'll be absolutely fine.
If you still feel worried, talk to your family about it. Or even your friends.
It's much better to tell someone how you feel than keep it bottled up.
I hope this helps, and you'll be fine! Don't worry. :) x
· 8 years ago