A bird in the hand is worth two in the bush refers to the value of something that you have worked hard for which is worth more than double the item if you haven't worked hard to get it.
If you take the phrase literally, then a bird in the hand would be a trained bird. It would have had a lot of effort and time taken to get the bird to be tame and to be sitting in your hand. Where as two birds in the bush would be wild and have little value as they would not sit in your hand and be worth less to you than the tame bird.
Therefor take this meaning and look at it in life. For example if you work hard to pay off your car, you will look after it and service it, make sure it always looks clean and tidy. If you get gifted a car or win it, i.e don't earn it, then you are less likely to look after it because you'll see no hard earned value in it. So something that you have worked hard for is worth more than something that you haven't.