Dear Ariane,
I'm sorry to hear that you are feeling so afraid and so distressed at the moment.
As Alex says, change is happening all the time anyway, no matter what you're wishing for. All of your life is a constant process of manifesting. Don't worry - just because you wished for something positive in your life and something painful happened to manifest alongside it, this doesn't mean that they are therefore linked. And it definitely doesn't mean that you are in any way the cause. So you have nothing to be afraid of. As Eagle says, you fundamentally have no control over others - everyone is on their own path.
As Alex suggests, by focusing on positive feelings, perhaps this will open you up more to the manifestation of positive feelings and experiences in the future which could of course take forms you might not expect. In this way, you are leaving the detail to the universe - and it will respond in the way that is best for you and for those around you. Don't take that level of responsibility onto yourself.
I am so sorry for your loss and it is quite common to experience negative and particularly guilt-related feelings when you are grieving. These will pass though, so be gentle with yourself and make sure to draw on support from those around you when you feel like you need it. It's easy to feel isolated, but there is always help around you if you call out for it.
I send you much love.
best wishes
Ingrid