Nowdays due to pilot shortages if you have a nasty flight ( very early morning with multiple legs) , pilots report sick in the evening, report fit in following noon and do a cushy evening flt !!
Bhoju, unfortunately that kind of attitude does you no favours amongst your colleagues who are on standby or, if your crewing department are in the habit of messing other pilots lives around, they will just change someone elses roster to cover the unpopular flight that you have avoided by pulling a sickie. That other person probably has their roster messed about and they just end up picking up all the dregs that you have left them.