This concept is what comes to my mind when we think about ourselves versus other people, especially when we are in dire straights. Taken to the extreme, it can morph into idolizing other people. The mistake is that we forget God, our Higher Power, The Creator as being the ultimate player in our lives.
I think this phenomenon happens most with people who have been battered or victimized. My history as an orphan has warped my view of people and my relation to them. If I didn't have a healthy faith in God, my relationships would be either non-existent or sorely unfulfilled. In fact, until I "found" God, I relied too heavily on people; the logical fear response to being abandoned. God doesn't blame me for that period of my life, or yours.
The problem with overestimating (relying) on people is that it's quite a burden/load to bear. But God's word says: “Come to me, all you who are weary and burdened, and I will give you rest. 29 Take my yoke upon you and learn from me, for I am gentle and humble in heart, and you will find rest for your souls. 30 For my yoke is easy and my burden is light.” (NIV)
So, it's not that we have to tow the load all by ourselves, but we need to be wise about how we manage it and who we have to help us. Many times we first lose hope in ourselves, and that's when we underestimate our strength. Not to say that we will be strong in all things. But God has gifted us unique talents and skills; and when we use those skills for his will, we will be boosted to heights unknown and unfathomable.
When we lose faith in ourselves, perhaps it is because we believe too much in ourselves and not enough in God. When we cannot rely on ourselves, naturally, we lose esteem in ourselves. But with God's love and strength, self esteem is of no consequence- faith is everything. When we take the burden off our friends, lovers and family and let God take his rightful place, those relationships have space to grow and be positive. And when we humble ourselves to the fact that we have little strength in comparison to God, we give ourselves the grace during our follies and mental space to try and try again WITH God's help.
When we assume that a spouse of an alcoholic should be able to handle all things since that person isn't debilitated by alcoholism, we are overestimating their strength. Sicknesses like alcoholism take huge tolls on the family members as well. That is why they created Al-Anon for the family members of alcoholics. That is why there is a relational dynamic called "co-dependency." That is usually the hell that people in those harrowing circumstances live without dependence on God for peace, hope, and strength.
Depending on the degree of closeness to a burden such as addiction or depression, the people closest to that sufferer also suffer. We must reach out to all who are impacted by those things. They affect how people take care of themselves, how they parent, how they live. The impact is much wider than we know.
So rather than under or over estimating people, let's do our part to pray for them (extend a helping hand) and hopefully lead them to God. And some people are beyond words or coercing. They're at the stonewalling stage. For those situations, consider this verse: "Wives, in the same way submit yourselves to your own husbands so that, if any of them do not believe the word, they may be won over without words by the behavior of their wives." 1 Peter 3:1 NIV Actually, anyone can be "won over without words." Part of that idea involves vigorous prayer and conversation with God, rather than that suffering person.
The Enemy will do his part to convince us that we don't need God and we can do things on our own. The Enemy will try to convince us that people CAN be relied on (or help) but they are just unwilling. The Enemy will do everything to sever our relationships to isolate us and take us for the spoils. But in those moments, cry out that you are not on the enemy's team. Send the enemy away with your prayers and words from the Bible.
But, always remember to thank God for his words (Bible), his love, his concern for you and everyone you love. With God, we can only underestimate his power and willingness to be a positive part of our lives. Hallelujah!