Do what you can. ‘Can’ means with all your effort and struggle. Not what you ‘want’. :)
When I get to know about something that Allah likes, for example Tahajjud prayers, I try my best to do it. And I overdo it. :D
Meaning, I start off with so much energy and ‘josh’ that I can’t continue it. It becomes impossible for me to carry it on with regularity.
What I’m trying to say is, whatever good you decide to do, be realistic and not too emotional. Start small, go big slowly. As for me, I should start with two rak’aat of Tahajjud and increase the number with time, inshaAllah. So it’s easy for me to carry it on and do it regularly. Why do I talk about regularity in good deeds? This Hadith will tell you..
Once the Prophet came while a woman was sitting with me. He said, “Who is she?” I replied, “She is so and so,” and told him about her (excessive) praying. He said disapprovingly, “Do (good) deeds which is within your capacity (without being overtaxed) as Allah does not get tired (of giving rewards) but (surely) you will get tired. And the best deed (act of worship) in the sight of Allah is that which is done regularly.”
A deed done regularly, though less in quantity, is more beloved to Allah than the deed which is more in quantity but not done regularly. (I had problems constructing that sentence. Hope the message is through. :P)