How can one generally prevent silly mistakes in very long physics calculations? I am a student working on certain open-ended research problems in quantum systems that mostly have long calculations and deal with a large number of terms. I tend to make a lot of silly mistakes despite taking utmost care not to do so. By the time I discover I have made a mistake, I have to begin everything from scratch. This takes up a lot of useful time and is extremely frustrating. Also since these are open-ended problems I cannot refer to anything to check whether my calculations are correct.
Is there something I can do or practice to prevent such things?
 A: What I do is, before beginning super long multi-part calculations, I establish certain conditions that must be upheld by the equations at each step. For example units, or symmetry in certain variables.
In a calculation I'm doing right now, I spent a couple days working out an important simple case in excruciating detail. Now that I'm doing the full calculation, I can map each stage of the calculation to the simple one and make sure I get the right answer in the appropriate simplifying limit.
This is similar to debugging in programming, doing sanity checks along the way.
A: I personally find organization and alternate methods help me avoid my mistakes. When working on long calculations, I'll often split my equation into numbered chunks. Below the equation, I'll label the section I'm working on, then solve it in a very organized manner (generally one line per step with apparent algebraic steps). I'll then double check my work, and if there's an alternate method of solving it, I will go through that one too and check both my answers. For intermediate steps, I box or star important equations I may need later. Be really careful and double or triple check negative signs. Hope this helps.
