When things break apart, don't always look up the road, be aware of whats back. Sometimes it's more rewarding to go back to a fellow rider that's also just off the pace but of a similar ability to you, and work together or the stronger rider do a little more work and both get to the goal a little faster, a bit safer and with allot more satisfaction.
In the end you go to group rides to ride together, so look around you and even when the pace lifts, ride for one another, it's not only the strongest riders that can be patrons of the peleton, but across the whole group.
When the pack size increases we need to increase our vigilance. Those with experience, keep an eye on the group, pull em into line if need be, and set a reasonable pace to keep the buch moving. Don't accelerate to hard of the lights, smooth and even, so people are not sprinting back on then decelerating. Leave an extra buffer between you and the rider in front if need be. Use hand signals often but wisely, parked cars are a must signal, pot holes/glass always, and stopping or slowing. To late to signal call it. Pass the signal on to riders further down the pack. FS