Look back at your life.

There might have been some time in your life when u had felt horrible and u thought that u r going to feel the same for the rest of your life.

But now ur mind is off that issue. Similarly, when these horrible thoughts of yours come to your mind, always keep in mind that these are mere thoughts, they have nothing to add to reality, nothing to take away from reality.
And keep in mind, that this will finish after some time.

I am in the very same position right now, i feel really horrible about loosing my friends, and my thoughts go to the maximum depression, but it can always be controlled if i keep telling my mind that these feelings are false.