παρακαλοῦμεν δὲ ὑμᾶς, ἀδελφοί, νουθετεῖτε τοὺς ἀτάκτους, παραμυθεῖσθε τοὺς ὀλιγοψύχους, ἀντέχεσθε τῶν ἀσθενῶν, μακροθυμεῖτε πρὸς πάντας.
But we encourage you, brothers, warn the insubordinate, console the discouraged, hold fast to the weak, have patience toward all.
In this passage Paul is exhorting the Thessalonians to warn those who are not submitting to church leadership, to console (or comfort) those who are loosing hope, to hold firmly to those who are/are becoming spiritually weak, and to be patient in the process.
Most translations render the term I've here translated "hold fast" as " help" or "be mindful of." The problem with these translations is that they don't, without further study, give us the impression that more is required of us than quick prayers and passing encouragements. This term literally has the meaning of holding on to something firmly. It is the same word used to describe the way we should "hold fast" to truth (Titus 1:9), and to God (Matt. 6:24; Luke 16:13). While the term can be used to mean simply "help," Paul never uses it that way, and neither does any other New Testament author.
When someone in our midst is falling, it is our responsibility to take hold of them and bring them along with us. In some cases this will mean praying and passing along encouraging words, but other times it will mean carrying their burden(s) with them. If you are feeling strong today, look for an opportunity to be God's provision in the life of someone who is struggling. If your brother or sister in Christ is too wounded to traverse the narrow path today, carry them forward on Christ's shoulders until their faith has healed the wounds.