Make sure you give your wife a great farewell. If there is still plenty of time left before she is to leave, do not waste it by procrastinating. Instead, use it to make better preparations for her farewell.
On the night before she is to leave, take her out for dinner to an expensive restaurant. If you cannot afford taking her to an expensive restaurant, just take her to one of her favourite restaurants. You can later go spend some time together in the park. Hold her hands while walking or sitting on a bench.
If you are feeling sad because she is going away for some time, there is no harm in crying and feeling sad. However, try not to cry too much in front of her, as that would make her feel sad and even guilty to an extent. Your sadness may end up ruining her trip.
Once she has left, do not think too much about how much you are missing her. Distract yourself with TV or some household chore that needs to be done.
If you cannot keep yourself from thinking about her and missing her, give her a call. It is perfectly fine to contact your wife while she is away. In fact, she will really appreciate it if you do call her, since it will let her know just how much you love her and miss her. You can text them “Good Morning Sweetheart” after waking up every morning and “Sweet Dreams my Love” before going to sleep. Just avoid calling or texting her too frequently.
Rather than just sitting at home and waiting for your wife to return, start going out a bit. Visit your family or hang out with your friends.
Think happy thoughts to keep the depression from taking over.