Salaam. What I would advise is that when your feeling doubtful in life you're not trusting Allah enough. When Allah has a plan for everyone. It's because it's in their best interest not to harm them or that they can't pass the test. We however because of our urge to be impatient we like to everything to come easy and quickly. Nothing in life comes easy, and we have to remember that patience is something we get rewards for. So remembering the rewards you receive and the fact that Allah knows best should indeed be enough. Don't over question it. Because that's what making you was was. And indeed you're questioning the creator. Yeah just remember that!!