"Do not be unequally yoked together with unbelievers. For what fellowship has righteousness with lawlessness? And what communion has light with darkness?" 2 Corinthians 6:14
We're not talking about eggs here, obviously. In biblical times, a yoke was a harness that was put on a pair of animals in order for them to walk and pull a heavy load together. Do you think that a grown, average size ox would want to be harnessed to a calf? If that scenario were to occur, what would happen? Most likely, the grown ox would end up dragging the calf. They would not be working equally, and both of them would be uncomfortable.
That statement can easily be related to the dating world today. Missionary dating lures many sons and daughters of God into places they were never intended to go. Some would argue, "Well we are supposed to reach the lost, aren't we?" Yes, we are! I recently heard a statement at a conference I attended and one of the speakers said "Jesus didn't have to flirt with the woman at the well." At this point, you can imagine the crowd contributed a loud "Ooooohhhh", because it's true. The great commission is no excuse to date someone who is on a completely different spiritual level than you or someone who has no relationship with Christ at all.
Today we have such a skewed view and often think, "I can change them." I hate to burst your bubble, but you can't. Jesus can, but you can't. The only way to the Father is through Him (John 14:6), not you. Being a light in someone's life is what we are called to be, I believe that with every fiber of my being. I also believe with equal certainty that you do not have to date someone to witness to them.
When you are in a relationship with someone, or "yoked" together, you are a team with the ultimate goal of marriage in mind. You are getting to know that person as you pursue them, and you are growing together in Christ. If in a relationship with someone that is not equally yoked with you, the scenario will most likely be the same as the ox and calf I mentioned earlier. One of you will be trying so desperately hard to encourage a relationship with Christ, and the other will be dragged. Work will not be equal, and both of you will be uncomfortable. Mindsets will not be the same, wants/needs in the relationship will not line up, and it will be a push/pull of values. Doesn't sound fun, does it?
I encourage you to not fall into the trap of missionary dating. Don't settle or lower your standards just because you can't seem to find somebody who relates to you. Keep your eyes locked on the Father. I can't say it enough: He is faithful to provide. God knows what He's doing; His timing is perfect. Don't jump into a relationship with lowered standards with someone to avoid being lonely. Be patient, witness to others and intercede for the lost, obey God's word and wait for the person who is equally yoked and grow together.