When we get tired, stressed, lonely, upset, emotional, hungry, etc., we are more easily persuaded to give in. This is why we see Satan tormenting Jesus after his 40 day fast. Jesus was weak and emotionally drained. It only takes us a couple days and we are emotionally drained. Some people have been in abusive relationships/work environments for years, or suffering illegal/legal drug abuse for years. They are tired and weak.
How do you find your strength? Paul is saying that we need to find "spiritual fathers". Those that will keep our eyes on Christ, those that will walk us through some dark times in our lives. Those that will give us sound scriptural doctrine when we become weak. If you do not have a Spiritual Father or Mother. Find one. Today. Don't just let this be anyone...you can't trust words...you have to see Christ.
1 Corinthians 4:14-21New International Version (NIV)
14 I am writing this not to shame you but to warn you as my dear children. 15 Even if you had ten thousand guardians in Christ, you do not have many fathers, for in Christ Jesus I became your father through the gospel. 16 Therefore I urge you to imitate me. 17 For this reason I have sent to you Timothy, my son whom I love, who is faithful in the Lord. He will remind you of my way of life in Christ Jesus, which agrees with what I teach everywhere in every church.
18 Some of you have become arrogant, as if I were not coming to you. 19 But I will come to you very soon, if the Lord is willing, and then I will find out not only how these arrogant people are talking, but what power they have. 20 For the kingdom of God is not a matter of talk but of power. 21 What do you prefer? Shall I come to you with a rod of discipline, or shall I come in love and with a gentle spirit?