This is something very practical. Don't complain. Be thankful. I believe God is continually at work. Whatever we are going through, He is using it to bring us closer to where He wants us to be. The way to embrace that and align with Gods will is to be thankful. Just exactly what 1 Thessalonians 5:18 says "Give thanks in every situation because this is God’s will for you in Christ Jesus."
But what happens many times is we complain about it. Complaining just puts our heart in position of lack. When we complain, we are saying our life lacks something. Basically says I deserve something I am not getting or I don't deserve something that I am getting. Either way, when you complain you make a choice to hold yourself back from all that God has for you. Kevin Elko taught me a phrase that I love. When you complain, you remain. But when you praise, you raise. Don't complain when you don't get a promotion, be thankful for the job you do have. Don't complain when you don't play that day, be thankful that you are on the team & able to have a chance at all. Don't complain about the loved ones you've lost, be thankful for the loved ones you still have. We make a choice to complain or be thankful. Do what Jesus says and watch His will unfold.