"Jesus is Lord" is what is called a performative statement, and says something how one regard one's own life in light of the life of Jesus. It is a declaration not only about reality but also a declaration concerning how the speaker really wants to live.
If we stand back and look at Jesus' life, his interaction with people, his preaching, and ministry as a whole, we hold that the defining characteristics of the Father whom Jesus revealed is love (John 3:16; 1 John 3-4). And it is from that characteristic that the simplicity of the Gospel, of all of Scripture and human history has its foundation. It is from that characteristic, Love, that calls us to love Him and the other. After all, God is not willing that anyone should perish but that all should come to repentance (2 Peter 3:9). Further, Jesus is, present tense, sent into the world as Saviour to forgive us and to reconcile us to himself (2 Cor 5:19). Jesus says his Father has rendered all judgement into his hands (John 5:22), and yet Jesus also said that he did not come to judge to condemn (John 8:15; 12:47) but to extend unilateral mercy, which trumps all judgement (James 2:13).
In short, if we make the declaration that Jesus is Lord, we proclaim truth, simple as that. But we also declare that His sending us into the world ought to affect every choice we make from than on (Col 2:6). We become obedient to the values and goals of the Kingdom of God Jesus established.
But by declaring Jesus as Lord, we also affirm that God sent him not to judge the world but to safe the world (John 3:17). We affirm His ministry of reconciliation and the relational aspect thereof over our tendency to judge and to distance us from the exact people Jesus came to safe, sinners (Luke 5:32). By declaring Jesu as Lord, we not only following him, but his mission has become our mission also, to go and to seek the lost (Matt 28:19) and to teach them (Matt 28:20).
Finally,, by declaring Jesus as Lord, we also affirm that Jesus is not simply an influential person of the past that extends into the present time, like Paul or Peter, or Gandhi to name only a very few, but a person of the present, in the present, here and now (Matt 28:20)>