We feel your pain. As a person filing his own taxes for approximately 20 years, and a close observer of my tax returns for several decades before that, I've seen capital gains rates and overall tax rates fluctuate. But overall they are lower on long-term gains than ever before in my long experience. But not so low for short-term gains. If you are an active trader, I expect much of your gains were short term. On that, my only immediate advise is to take a close look at and consider the length you have to hold investments before you can claim the longer-term (lower) capital gains rates before selling an investment.
On the moral support side, consider that, as you say, markets go up and down, and using this year so far as example only, if you bought an investement late last year and sell now, you would probably have a capital gains loss for next year's tax purposes, which should reduce your taxes owned, assuming you have other taxable income, a year from now.
Finally, I remember income averaging, which reduced the tax load for people getting a one-year only exceptional income boost. That provision went away. Speak to your congresspeople, Senator's offices to express your views on bringing that back. They might tell you overall rates are lower than they were in the days of income averaging, and that is true; but still, for more average tax payers, income averaging would surely help more for those who sell their sole long time residence and have big capital gains on that. Maybe not so helpful as lower overall tax rates for those taxpayers who have multiple residences, major ongoing investment or income generating holdings, so have a large income almost every year. Hmm.
