Sleep is a natural meditation anyways. --though the meditation we are learning is more 'active' in the sense we learn how the Spirit works through emptiness to heal our channels(and in 'time' we learn to connect with our Spirit by trust and love) Don't worry if you fall asleep during/near the end of the meditation, you'll be fine.
The channels open in deep rest, relaxation and sleep, and are re-orginized (to some extent) on their own. (which is why you don't really want to eat a heavy meal before going to sleep) Meditation takes it a step further and allows you the opportunity to work with the 'extra energies' that your sub-concious didn't fully work out during normal sleep. In addition, time you spend in meditation can be substitute (partially) for sleep.
The Universe takes care of you, and only brings you lessons that you choose. Let go of the idea of 'losing energy' *can be* a silly belief more than anything, (notice how I said 'can be') You are connected with the Universe so any 'lost' energy will be made up for at some 'other time' (it's going where it's needed). However, if you are concerned with that aspect and would rather have a more 'consistant balance' (rather than like a see-saw)...
First 'let go' of the idea of 'losing energy' (yes keep doing the closing excersises, it's "likened to" turning off the faucet in a way) In my 'perspective' I have to close the energy, not because I 'lose', I've sometimes got 'too much' when I forgot to do the closing.
Then, you could 'write yourself a message' such as:
"After meditation, my dantien will automatically complete the closing/ending steps. My purified/healed energy will be with me."
Keep it simple for effectiveness. The unconcious can behave computer-like and takes things litterally sometimes.
Don't use words like "should, don't, won't" or 'negetive' concepts' in general. Keep 'no' and 'not' out. For example, don't say: "I will not lose energy" but rather "I will keep my renewed energy" is much more appropriate. It's not a 'negetive concept' and you are using "I will" which further strengthens your cause.
Also, don't use 'and' if possible. Keep sentences reletively short and simple, as if you are giving your computer brain instructions.
Say this affirmation to yourself 3 times, (you say do it outloud if that helps your affirmation even more) Feel that your subconcious got the message and trust that it will carry out your instructions (it will). After doing this for a few practices, you may notice you don't really need to 're-affirm' the message with words, but you get an 'energy feeling' of what the message is. This non-verbal, 'energy feeling' of the message/affirmation *is* actually the 'thought-form' of your affirmation's instructions "compiled" (like computer code)
(congrats you've just communed with your subconcious!!) when you need, you can just recall the feeling, thank your subconcious and go about your meditation.
(you can also 'un-install' old thought-forms, by using energy techniques/visualizations) so if you come across a 'negetive belief' or 'someone else's program' you can just "not put energy into it" and let it go 'as energy'
~Z