Okay, I'm probably stating the obvious here but you really shouldn't look a gift horse in the mouth, as the saying goes.
Basically, if you want to make it as a freelancer, you don't turn down any opportunity if you can help it. On occasion I have inevitably had to turn work down due to clashing commitments or a simple (yet cruel) lack of time. But they have been a few close calls where I might have missed out on other opportunities if I hadn't said 'Yes' to an earlier project.
Can you believe I almost missed out on the chance to have Bloodbones published by Wizard Books? Steve Jackson and I first communicated about the possibility over a year before it finally happened but I was planning my wedding at the time and didn't get back to him soon enough. As a result, Sword of the Samurai and Talisman of Fear were re-printed before Bloodbones ever saw the light of day. Thankfully I got a precious second chance and this time seized it with both hands. Who knows, if I hadn't there might never have written Howl of the Werewolf, Stormslayer or Night of the Necromancer.
When I was first commissioned to write my Doctor Who gamebook The Horror of Howling Hill it was supposed to feature Donna Noble and not Martha Jones. Having got my manuscript on in time, Penguin then changed their publishing schedule. If The Horror of Howling Hill was ever to see print I had a matter of days in which to re-write it so that it included Martha and not Donna. I did and as a result got the chance to write a Star Wars The Clone Wars gamebook - Crisis on Coruscant - and my most recent Doctor Who chapter book Terrible Lizards.
So, I guess what I'm saying is that make the most of every opportunity you can because you never know where it might lead.