A marathon in 4h40m? Who cares?

Hurrah! Today I've run my first proper run at work. I managed 5 laps of the 0.7 mile circuit¹, in a pretty consistent ~7½ minutes per lap. This is back to the sub 11-minute miles I'd achieved before picking up my injury:

0.7 Mile 1 - 7m12s
0.7 Mile 2 - 7m25s
0.7 Mile 3 - 7m38s
0.7 Mile 4 - 7m32s
0.7 Mile 5 - 7m36s

If I were able to keep up this kind of rhythm for seven times this distance (does 26.2 miles sound a bit shorter put like that?!) then I'd be well on target for the marathon in under 5 hours. Not that that's my target anymore. You know I set four targets back in November? Well now my targets are slightly revised:
Target 1 - just to finish (however long it takes!)
Target 2 - just to finish (however long it takes!)
Target 3 - just to finish (however long it takes!)
Target 4 - just to finish (however long it takes!)

Yep - I have one target and one target only. To finish. Yes it would be great to do it in under 4½ hours, but it doesn't matter if I do in in 4, 5 or even 6 hours. As long as I can actually get round in one piece, and finish the whole 26.2 miles, then that is the only achievement that matters. The reason for my change in thinking?
Simple. Thanks to some advice from this book. By April I will have been training for the marathon for 6 months. I will have run over 300 miles to get there. I will have raised over £1500 in sponsorship for VRH, and also run a half marathon too. Do I really want to risk even the slightest feeling that all this has been a failure - just because I'd set myself a target of 4½ hours, and I only managed it in 4h48m? in 5h06m? in 5h42m? So out with the targets, and in with the positive mental attitude. I'm not out to win the marathon, am I? I'm out to do it, and do it I will!!

¹ actually the route is nearer to 0.77 miles, but I'm rounding it down to 0.7m to make the maths easier!!