I never thought of contentment as a gift from the Lord. As humans, contentment does not come naturally. Our lot is to work and toil under the sun. Believers are to work as unto the Lord day in and day out and rejoice in the work He has given. We must be willing to confess the discontentment weeds that creep within our heart and pray that God would give grace for the struggles.
When we find joy that true contentment brings it overflows and protects us from finding things to complain about. This takes practice and a surrendered heart to the Lord. Just like it takes work to get that soil right and rich in order to grow that garden. We must take complaints (weeds) and give them to the Lord and ask for Him to give us contentment in all circumstances.
Being content doesn't depend on my situations but instead my heart and posture toward God. If I'm out of alignment with Him then my heart focus isn't right and I will proceed to complain and basically focus on myself and my problems.
Just like when our soil isn't rich with proper nutrients that garden isn't going to grow big beautiful plants. Because of Christ we can be satisfied and love on Him through our life under the sun.
Forgetting God makes a person a life-long complainer. What Christian wants to be known for that?! We find the only real and true contentment in Christ alone. We must seek Him and ask him to give us the often missing nutrient of contentment (even when we are struggling) in order for us to grow a garden of gratitude.