Based on my experience of the effect this sort of behaviour from a father has on children (my own dad to me, and my ex-husband's to my daughter), I beg you to stop behaving like this. Whatever disagreements you have with your ex, DON'T take it out on your kids.
If money is tight and you genuinely can't afford things their mother would like for them, be honest and open about that, but also consider that some events are once in a lifetime and may be worth extending yourself for.
Don't waste the limited time you have with your children - both in terms of your scheduled visitation, and the years of their childhood overall - making it all about you and how disappointed, bitter and angry you are. Find things to do with them that you all enjoy. Keep in touch outside of the time you physically spend together. Offer to be there for them in whatever way you can, and follow through on that offer. Accept that sometimes kids won't want to hang out with their parents and would prefer to spend time with their friends - even if they love their parent to bits, but more so if a parent comes across as angry and judgemental and makes spending time with them unpleasant. Sure, if there are things they do that you consider rude or thoughtless, you can discuss that with them - if you're prepared to do it in a constructive way, and accept that regardless of their age they have their own perspective and a certain right to autonomy. Most importantly, don't make your kids feel as if your love, attention and help is conditional on them measuring up to some arbitrary standard that you determine is "good enough". That's not love.
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If money is tight and you genuinely can't afford things their mother would like for them, be honest and open about that, but also consider that some events are once in a lifetime and may be worth extending yourself for.
Don't waste the limited time you have with your children - both in terms of your scheduled visitation, and the years of their childhood overall - making it all about you and how disappointed, bitter and angry you are. Find things to do with them that you all enjoy. Keep in touch outside of the time you physically spend together. Offer to be there for them in whatever way you can, and follow through on that offer. Accept that sometimes kids won't want to hang out with their parents and would prefer to spend time with their friends - even if they love their parent to bits, but more so if a parent comes across as angry and judgemental and makes spending time with them unpleasant. Sure, if there are things they do that you consider rude or thoughtless, you can discuss that with them - if you're prepared to do it in a constructive way, and accept that regardless of their age they have their own perspective and a certain right to autonomy. Most importantly, don't make your kids feel as if your love, attention and help is conditional on them measuring up to some arbitrary standard that you determine is "good enough". That's not love.