He symbolises wisdom, strength, valour and above all, humility. What happened in Ramayana happens in the life of everyone. This is a universal fact. Power in the hands of those void of wisdom leads to a bloated ego. A bloated ego leads to lust.
Lust leads to anger.
For Lakshmana, the order of his brother was supreme. He accepted the word of Rama not to use the asthra. And he did not use it, at the cost of his very life. Rama restrains Lakshmana from using the Brahmastra against Indrajit. It puts almost all chief characters of the epic under test.