Rejoice in the Lord always; again I will say, rejoice. Let your reasonableness be known to everyone. The Lord is at hand. Philippians 4:4-5 (ESV)
"Christians believe that God is sovereign over all things, including even those circumstances that they find unpleasant and undesirable. When we complain and grumble, we are telling those around us that we believe God is doing a very poor job, and, if given the opportunity, we could do much better."
Philippians 2:14 tells us to do all things without grumbling or complaining. Boy, is that hard? It is so easy to find something wrong with, well, just about everything! But, if we desire to live a life filled with joy our attitudes must be joyful not disgruntled. Living joyfully doesn't mean your life is perfect or that everything turns out your way. On the contrary, having joy usually comes when we resolve that things aren't going our way, and that's ok. When we recognize God's rule over our lives, we can be content, even joyful about our circumstances, relationships and challenges, knowing that the all-powerful, all-knowing supreme authority of the universe has our best interest and His kingdom expansion planned out perfectly. This should give us joy!
Quote from: Ellsworth, R. (2004). Opening up Philippians (41-47). Leominster: Day One Publications.