I don't know how old you are, but you seem to ask a sincere question, and a good one. Perhaps you are someone young who doesn't remember the Reagan Presidency, but who has heard some things about "Reagan deficits"? I'm just guessing, but your question seems to suggest this possibility.

I recall that Reagan begged and pleaded constantly with Congress to reduce or at least limit spending, threatening at times to veto budget bills, which he did at times (but in my opinion, not often enough). Congress, and especially Speaker of the House Tip O'Neil, largely ignored him and refused to cut spending. Reagan was practical enough to know that if he refused to play with the Democrat-controlled Congress, he would get nothing. So he compromised. I consider that to be a mistake, but who knows?
George W. Bush, on the other hand, had a different attitude from day one. Before he was elected, in Jan. 2000 during the New Hampshire primaries, he criticized the Republican Party for its traditional stand on limited government (ie., economic responsibility). This was a completely different attitude from Reagan. This new attitude has been stated by Vice President Dick Cheney with the mantra attributed to him that "deficits don't matter". George Bush, unlike Reagan, had both a Republican House and Senate, and yet they exploded the deficits as if they "didn't matter". In my mind, this was inexcusable. But that's the difference.
During the Reagan Presidency, for every presidential signing of a budget, it required literally dozens of Democrats to vote for those same budget deficits. DOZENS of Democrats! Yet today, these same Democrats who voted for every single one of those deficits try to spin history and refer to them as "Reagan deficits". I can only think of one word to describe this phenomenon: hypocrisy!
Article 1, Sections 7.1 and 8.2 of the U.S. Constitution explicitly state that spending, revenues, and debts of the U.S. government are the responsibility of the Congress, NOT the President. Congress is ultimately responsible for the budget, and thus, budget deficits. The Constitution lays responsibility for budgets -- and their deficits -- where they belong, at the feet of the U.S. Congress. This responsibility applies equally to Republicans (during the Bush Presidency) and Democrats (during the Reagan Presidency). Both Parties are, I believe, equally to blame!