In life, most people have their share of good fortune and tough times. Some seemingly have a little more than one or the other, but in my observation, most have a balance of both over time. It is good to remember this in times good and bad. When times are good, enjoy those times, and when times are bad, know that there are better days to come.
Sometimes this good-bad situation can create havoc. This is especially true when one friend or loved one is experiencing something incredibly good and another is experiencing something incredibly bad. It's difficult for the challenged person to recognize the happy person's joy and visa versa, and that's natural. When times like this happen, the most natural step is to be as supportive as you can and make some space to be in your happy or not so happy space. Finding the comfort of those who understand the situation you are in is always helpful at times like these.
Don't let others rob you of your joy--enjoy it. Similarly in your tough times, remember to let others enjoy their good times. There will be highs, lows and plateaus in life, and it's best to learn to navigate this terrain as best you can. Onward.